Module
04.(B1) Electronic Fundamentals
1.1a.
Semiconductors - Diodes.
Question
Number. 1. What gives the colour of an LED?.
Option
A. The active element.
Option
B. The plastic it is encased in.
Option
C. The type of gas used inside it.
Correct
Answer is. The active element.
Explanation. The
active element is the element used in the doping of the semiconductor
material. Aircraft Electricity and Electronics 5th Edition Eismin
Page 121.
Question
Number. 2. A germanium diode is used for.
Option
A. rectification.
Option
B. voltage stabilization.
Option
C. modulation.
Correct
Answer is. rectification.
Explanation. Germanium
diode has the least forward bias voltage drop and is best for
rectification.
Question
Number. 3. Why is a diode put in parallel with an LED?.
Option
A. To protect it from AC.
Option
B. So it will work only above a certain voltage.
Option
C. So it will work only below a certain voltage.
Correct
Answer is. To protect it from AC.
Explanation. An
LED has a high forward bias voltage drop but is easily damaged when
reverse biased. AC is therefore not good for an LED.
Question
Number. 4. When testing the forward bias of a diode with a
multimeter.
Option
A. the positive lead of the ohmmeter is placed on the anode.
Option
B. it does not matter which terminal the positive lead of the ohmeter
is placed.
Option
C. the positive lead of the ohmmeter is placed on the cathode.
Correct
Answer is. the positive lead of the ohmmeter is placed on the anode.
Explanation. To
test forward bias, the positive lead of the multimeter must be placed
on the anode. Note: If the question says 'moving coil meter' then it
would be the negative lead on the anode, since the negative side of
the battery in such a meter is connected to the + lead. Aircraft
Electricity and Electronics 5th Edition Eismin Page 113.
Question
Number. 5. This is a diagram of.
Option
A. an SCR.
Option
B. a TRIAC.
Option
C. a Schottky diode.
Correct
Answer is. an SCR.
Explanation. NIL.
Question
Number. 6. Which of the following describes the characteristics of a
Thyristor?.
Option
A. High voltage handling.
Option
B. High power handling.
Option
C. High current handling.
Correct
Answer is. High current handling.
Explanation. A
thyristor (such as an SCR) is a high current switching.
Question
Number. 7. Light Emitting Diodes (LEDs).
Option
A. emit light of only one wavelength dependent on type.
Option
B. have very wide viewing angles.
Option
C. are easily damaged if forward biased b more than 5V.
Correct
Answer is. emit light of only one wavelength dependent on type.
Explanation. NIL.
Question
Number. 8. In a semiconductor junction diode, electrons are the
minority carriers.
Option
A. within the P region.
Option
B. within the N region.
Option
C. in both the N and P regions.
Correct
Answer is. within the P region.
Explanation. NIL.
Question
Number. 9. A silicon diode, when compared to a germanium diode has.
Option
A. a higher forward bias voltage.
Option
B. the same forward bias voltage.
Option
C. less forward bias voltage.
Correct
Answer is. a higher forward bias voltage.
Explanation. Si
= 0.6V, Ge = 0.2V. Aircraft Electricity and Electronics 5th Edition
Eismin Page 111.
Question
Number. 10. This symbol is.
Option
A. a transistor.
Option
B. a diode.
Option
C. a triac.
Correct
Answer is. a diode.
Explanation. NIL.
Question
Number. 11. This symbol is.
Option
A. a photodiode.
Option
B. a laser diode.
Option
C. an LED.
Correct
Answer is. a photodiode.
Explanation. The
photodiode is used in reverse bias. The minority current increases
when light shines on it.
Question
Number. 12. A zener diode.
Option
A. allows current to flow in one direction.
Option
B. stabilizes voltage at a predetermined level.
Option
C. acts like a switch.
Correct
Answer is. stabilizes voltage at a predetermined level.
Explanation. Zener
diodes are usually used in voltage regulator circuits. Aircraft
Electricity and Electronics 5th Edition Eismin Page 385.
Question
Number. 13. A junction diode.
Option
A. is similar to a vacuum diode but cannot rectify.
Option
B. has one p-n junction.
Option
C. can handle only very small currents.
Correct
Answer is. has one p-n junction.
Explanation. NIL.
Question
Number. 14. Reverse bias.
Option
A. raises the potential barrier.
Option
B. lowers the potential barrier.
Option
C. greatly increases the majority carrier current.
Correct
Answer is. raises the potential barrier.
Explanation. NIL.
Question
Number. 15. A diode connected across a relay coil is used to.
Option
A. dissipate coil spikes on switch off.
Option
B. allow the coil to energize with only one polarity.
Option
C. cause a delay in switching on.
Correct
Answer is. dissipate coil spikes on switch off.
Explanation. Aircraft
Electricity and Electronics 5th Edition Eismin Page 121 reading
material.
Question
Number. 16. To check the forward resistance of a diode with a
multimeter, the lead connected to the positive terminal is put to
the.
Option
A. anode.
Option
B. cathode.
Option
C. either anode or cathode.
Correct
Answer is. anode.
Explanation. To
forward bias a diode with a multimeter, the positive lead must be
connected to the anode. Note: If it were a moving coil meter, you
must connect the negative lead to the anode since the positive end of
the battery is connected to the negative lead.
Question
Number. 17. A thyristor has which of the following?.
Option
A. A positive temperature coefficient.
Option
B. High resistance when switched off.
Option
C. High resistance when switched on.
Correct
Answer is. High resistance when switched off.
Explanation. The
thyristor (such as an SCR or TRIAC) is basically a switch which
provides a high resistance when switched off.
Question
Number. 18. What does the circuit shown do?.
Option
A. Full wave rectifier.
Option
B. Half wave rectifier.
Option
C. Voltage doubler.
Correct
Answer is. Half wave rectifier.
Explanation. The
diagram shows a half wave rectifier. The capacitor is for smoothing
the output. A full wave rectifier requires 4 diodes and a voltage
doubler requires two capacitors.
Question
Number. 19. In an LED, what is used to make the colour?.
Option
A. The plastic lens cover.
Option
B. The electrons.
Option
C. The doping material.
Correct
Answer is. The doping material.
Explanation. The
dopant is what gives the LED its colour.
Question
Number. 20. An atom with 5 electrons in its outer shell is part of.
Option
A. a C type material.
Option
B. a P type material.
Option
C. an N type material.
Correct
Answer is. an N type material.
Explanation. An
atom with five electrons in its outer shell (pentavalent) will
provide an extra free electron and make the material an N type.
Aircraft Electricity and Electronics 5th Edition Eismin Page 110.
Question
Number. 21. A thyristor is commonly used for.
Option
A. overvolts regulation.
Option
B. voltage regulation.
Option
C. rectification.
Correct
Answer is. rectification.
Explanation. A
thyristor (especially an SCR) is often used for rectification.
Question
Number. 22. A diode which emits photons when conducting is a.
Option
A. light emitting.
Option
B. varactor.
Option
C. zener.
Correct
Answer is. light emitting.
Explanation. Photons
= light, so a diode which emits light is a Light Emitting Diode.
Question
Number. 23. The electrodes of an SCR are.
Option
A. gate, cathode, anode.
Option
B. source, drain, gate.
Option
C. anode, cathode, source.
Correct
Answer is. gate, cathode, anode.
Explanation. The
electrodes of an SCR are the anode, cathode and the gate. Aircraft
Electricity and Electronics 5th Edition Eismin Page 120.
Question
Number. 24. What gives an LED its colour?.
Option
A. A gas.
Option
B. The cover.
Option
C. Composition and impurity of the compound.
Correct
Answer is. Composition and impurity of the compound.
Explanation. It
is the doping element which gives an LED its colour.
Question
Number. 25. Forward voltage of a silicon diode is.
Option
A. 1.6V.
Option
B. 0.6V.
Option
C. 0.2V.
Correct
Answer is. 0.6V.
Explanation. Si
= 0.6V, Ge = 0.2V Aircraft Electricity and Electronics 5th Edition
Eismin Page 111 or 113.
Question
Number. 26. What is the typical volts drop across an LED.
Option
A. 0.2V.
Option
B. 0.4V.
Option
C. 1.6V.
Correct
Answer is. 1.6V.
Explanation. An
LED volts drop is typically 1.6 - 2.4V. Aircraft Electricity and
Electronics 5th Edition Eismin Page 121.
Question
Number. 27. What diode gives off light photons when forward biased.
Option
A. LED.
Option
B. Gunn diode.
Option
C. Schottky diode.
Correct
Answer is. LED.
Explanation. LEDs
give off light (photons) when forward biased.
Question
Number. 28. The anode of a diode is connected to a +4V DC supply and
the cathode is connected to a +2V DC supply. The diode is.
Option
A. forward biased not conducting.
Option
B. reverse biased not conducting.
Option
C. forward biased conducting.
Correct
Answer is. forward biased conducting.
Explanation. Forward
bias is anode to cathode. 4V fwd bias and 2V reverse bias, the diode
is 2V fwd bias in total.
Question
Number. 29. Using electron flow in a diode the current flows from.
Option
A. Anode to Cathode.
Option
B. Cathode to Base.
Option
C. Cathode to Anode.
Correct
Answer is. Cathode to Anode.
Explanation. ELECTRON
FLOW (i.e. American notation) is cathode to anode (against the arrow
direction). Aircraft Electricity and Electronics 5th Edition Eismin
Page 111.
Question
Number. 30. When a hole diffuses from the p region to the n region.
Option
A. raises the potential barrier.
Option
B. it becomes a minority carrier in the n region.
Option
C. lowers the potential barrier.
Correct
Answer is. raises the potential barrier.
Explanation. The
potential barrier is formed by holes diffusing from the P region to
the N region, (and electrons diffusing from the N region to the P
region).
Question
Number. 31. A junction diode.
Option
A. can handle only small currents.
Option
B. is similar to a vacuum diode but cannot rectify.
Option
C. has one p-n junction.
Correct
Answer is. has one p-n junction.
Explanation. A
junction diode is so named for its one junction. Aircraft Electricity
and Electronics 5th Edition Eismin Page 111.
Question
Number. 32. A germanium diode.
Option
A. has a lower forward bias voltage than a silicon diode.
Option
B. has a higher forward bias voltage than a silicon diode.
Option
C. has the same forward bias voltage as a silicon diode.
Correct
Answer is. has a lower forward bias voltage than a silicon diode.
Explanation. Forward
bias voltage of germanium diode = 0.2 V. Silicon diode = 0.6 V.
Aircraft Electricity and Electronics 5th Edition Eismin Page 111.
Question
Number. 33. What switches off a thyristor?.
Option
A. Reverse bias gate.
Option
B. Remove the gate voltage.
Option
C. Remove supply voltage.
Correct
Answer is. Remove supply voltage.
Explanation. To
switch off a thyristor (such as an SCR) you must disconnect the
supply voltage. Aircraft Electricity and Electronics 5th Edition
Eismin Page 120.
Question
Number. 34. When an SCR is switched on it has.
Option
A. low resistance.
Option
B. no change in resistance.
Option
C. high resistance.
Correct
Answer is. low resistance.
Explanation. An
SCR is basically a switch, which, when switched on has a low
resistance. Aircraft Electricity and Electronics 5th Edition Eismin
Page 120.
Question
Number. 35. What type of pulse is required to switch on an SCR?.
Option
A. Positive.
Option
B. Negative.
Option
C. Positive or negative.
Correct
Answer is. Positive.
Explanation. A
positive pulse is required to switch an SCR on.
Question
Number. 36. A piece of pure Germanium.
Option
A. is electrically stable.
Option
B. has a deficit of electrons.
Option
C. has an excess of electrons.
Correct
Answer is. is electrically stable.
Explanation. In
a solid piece of semiconductor material, all the valence electrons
are occupied in the covalent bond. It does not conduct electricity.
Aircraft Electricity and Electronics 5th Edition Eismin Page 110.
Question
Number. 37. When a diode is forward biased, current flow is mainly
due to the.
Option
A. germanium bias junction.
Option
B. majority carriers.
Option
C. minority carriers.
Correct
Answer is. majority carriers.
Explanation. Forward
bias = majority carriers.
Question
Number. 38. When a diode is forward biased the.
Option
A. positive lead is connected to both N and P type.
Option
B. positive lead is connected to the N type and negative to the P
type.
Option
C. positive lead is connected to the P type and negative to the N
type.
Correct
Answer is. positive lead is connected to the P type and negative to
the N type.
Explanation. To
forward biased, connect Positive to P, Negative to N. Aircraft
Electricity and Electronics 5th Edition Eismin Page 117.
Question
Number. 39. The typical voltage drop across an L.E.D is.
Option
A. 2V.
Option
B. 4V.
Option
C. 6V.
Correct
Answer is. 2V.
Explanation. 2V
typical.
Question
Number. 40. What are the majority carriers for a forward biased PN
junction device?.
Option
A. Electrons and holes.
Option
B. Holes.
Option
C. Electrons.
Correct
Answer is. Electrons and holes.
Explanation. Majority
carriers are electrons in the N material, and holes in the P
material.
Question
Number. 41. Germanium in its pure state is.
Option
A. negatively charged.
Option
B. neutral.
Option
C. positively charged.
Correct
Answer is. neutral.
Explanation. Both
germanium and silicon are neutrally charged, even when doped.
Aircraft Electricity and Electronics 5th Edition Eismin Page 110.
Question
Number. 42. Which diode has a lower forward bias voltage?.
Option
A. Silicon.
Option
B. Germanium.
Option
C. Both have the same forward bias voltage.
Correct
Answer is. Germanium.
Explanation. Silicon
about 0.6V, Germanium about 0.2V. Aircraft Electricity and
Electronics 5th Edition Eismin Page 111.
Question
Number. 43. A Zener diode is used for.
Option
A. voltage stabilisation.
Option
B. rectification.
Option
C. voltage regulation.
Correct
Answer is. voltage regulation.
Explanation. A
Zener diode is used for voltage regulation. Aircraft Electricity and
Electronics 5th Edition Eismin Page 120.
Question
Number. 44. A thyristor SCR is a.
Option
A. bi-directional device.
Option
B. unidirectional device.
Option
C. multidirectional device.
Correct
Answer is. unidirectional device.
Explanation. http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/diac.html#c4
Question
Number. 45. What component is used to turn AC to DC?.
Option
A. Thyristor.
Option
B. Diode.
Option
C. Transistor.
Correct
Answer is. Diode.
Explanation. Although
a thyristor (SCR) can be used, a diode is more common. Aircraft
Electricity and Electronics 5th Edition Eismin Page 113.
Question
Number. 45. What component is used to turn AC to DC?.
Option
A. Thyristor.
Option
B. Diode.
Option
C. Transistor.
Correct
Answer is. Diode.
Explanation. Although
a thyristor (SCR) can be used, a diode is more common. Aircraft
Electricity and Electronics 5th Edition Eismin Page 113.
Question
Number. 46. What is an intrinsic material?.
Option
A. One with added elements.
Option
B. One with removed elements.
Option
C. A pure material.
Correct
Answer is. A pure material.
Explanation. Intrinsic
is a pure material.
Question
Number. 47. The voltage drop of a silicon diode is.
Option
A. 1 V.
Option
B. 0.7 V.
Option
C. 0.3 V.
Correct
Answer is. 0.7 V.
Explanation. Aircraft
Electricity and Electronics 5th Edition Eismin Page 111.
Question
Number. 48. A diode is parallel to an LED in an AC circuit to.
Option
A. provide correct amount of current for LED when circuit is switched
on.
Option
B. prevent back EMF in the circuit when LED is switched off.
Option
C. protect LED from AC current when switched on.
Correct
Answer is. protect LED from AC current when switched on.
Explanation. The
negative half cycle of the AC must be bypassed around the LED.
Question
Number. 49. In a forward biased diode, current is carried by.
Option
A. majority carriers.
Option
B. both.
Option
C. minority carriers.
Correct
Answer is. both.
Explanation. Forward
bias is both, reverse bias is minority carriers only.
Question
Number. 50. When checking a diode for reverse bias resistance the
positive lead goes to.
Option
A. anode and negative lead to earth.
Option
B. cathode and negative lead to anode.
Option
C. anode and negative lead to cathode.
Correct
Answer is. cathode and negative lead to anode.
Explanation. Positive
lead to cathode.
Question
Number. 51. Zener diodes are used for.
Option
A. Current control.
Option
B. Voltage control.
Option
C. Temperature control.
Correct
Answer is. Voltage control.
Explanation. Comment/Reference
(if available).
Question
Number. 52. Once started conducting an SCR switches off.
Option
A. only when the anode goes negative to the cathode.
Option
B. automatically after a specific time.
Option
C. only when the anode goes positive to the cathode.
Correct
Answer is. only when the anode goes negative to the cathode.
Explanation. NIL.
Question
Number. 53. In a forward biased diode, electrons leave the.
Option
A. the anode.
Option
B. the cathode.
Option
C. the doped area.
Correct
Answer is. the cathode.
Explanation. explainAnswer[3]="Electrons
jump accross the depletion layer from the Cathode (-ve) to the Anode
(+ve) to recombine with the holes and close the depletion layer".
Question
Number. 54. Diodes are.
Option
A. conductors.
Option
B. semi-conductors.
Option
C. Insulators.
Correct
Answer is. semi-conductors.
Explanation. Only
answer which is correct in both bias configurations.
Question
Number. 55. To function, i.e. conduct, a junction diode made of
silicon requires a forward bias of at least.
Option
A. 0.2V.
Option
B. 1.41V.
Option
C. 1V.
Correct
Answer is. 1V.
Explanation. Silicon
diodes require around 0.7V, so a is the closest.
Question
Number. 56. What is the average gain of an Op Amp?.
Option
A. 20.
Option
B. 200,000.
Option
C. 200.
Correct
Answer is. 200,000.
Explanation. NIL. http://en.wikipedia.org/wiki/Op_amp#DC_behavior
1.1b.
Semiconductors - Diodes.
Question
Number. 1. Tunnel diodes have the following characteristics.
Option
A. Heavily doped P-N junction with an extremely narrow depletion
region.
Option
B. Lightly doped P and N regions and a high reverse breakdown
voltage.
Option
C. Lightly doped P region, heavily doped N region and has a fast
response time.
Correct
Answer is. Heavily doped P-N junction with an extremely narrow
depletion region.
Explanation. NIL. http://en.wikipedia.org/wiki/Tunnel_diode
Question
Number. 2. The capacitance of a varactor diode is.
Option
A. inversely proportional with reverse bias voltage.
Option
B. a linear function of applied reverse bias voltage.
Option
C. directly related to the forward bias voltage.
Correct
Answer is. inversely proportional with reverse bias voltage.
Explanation. NIL. http://en.wikipedia.org/wiki/Varactor_diode
Question
Number. 3. A semiconductor doped with an element having a valency of
5 will produce.
Option
A. an N type material.
Option
B. either an N type or a P type depending on what type of
semiconductor material is used.
Option
C. a P type material.
Correct
Answer is. an N type material.
Explanation. Pentavalent
materials make an N type material due to its extra electron. Aircraft
Electricity and Electronics 5th Edition Eismin Page 110.
Question
Number. 4. In a diode clamper, if the resistor is removed making the
time constant equal to C x r where r is the reverse resistance of the
diode, this will ensure a.
Option
A. long time constant.
Option
B. short time constant.
Option
C. Very Long Time Constant.
Correct
Answer is. long time constant.
Explanation. NIL.
Question
Number. 5. PIN diodes are used mainly for.
Option
A. linear rectifiers.
Option
B. fast switching devices.
Option
C. voltage operated rectifiers.
Correct
Answer is. fast switching devices.
Explanation. NIL.
Question
Number. 6. To enable an IMPATT diode to operate correctly, it must
be.
Option
A. connected to a resonant circuit.
Option
B. used in its reverse bias mode.
Option
C. operated in its negative resistance range.
Correct
Answer is. operated in its negative resistance range.
Explanation. NIL.
Question
Number. 7. What type of diode would be used to stop voltage spikes
across a coil of a relay?.
Option
A. Gunn diode.
Option
B. Double acting diode.
Option
C. Schottky diode.
Correct
Answer is. Double acting diode.
Explanation. NIL. http://en.wikipedia.org/wiki/Voltage_stabiliser,
http://en.wikipedia.org/wiki/Zener_diode
Question
Number. 8. What is a schottky diode used for?.
Option
A. Rectification.
Option
B. Stabilization.
Option
C. Very high frequency applications.
Correct
Answer is. Very high frequency applications.
Explanation. A
schottky diode has very little junction capacitance and can be used
for very high frequency switching applications.
Question
Number. 9. When a hole diffuses from a p-region to the n-region it.
Option
A. becomes a minority carrier in the n-region.
Option
B. lowers the potential barrier.
Option
C. raises the potential barrier.
Correct
Answer is. raises the potential barrier.
Explanation. This
is descriptive of holes crossing the PN junction to form the
depletion layer. Aircraft Electricity and Electronics 5th Edition
Eismin Page 111.
Question
Number. 10. The junction barrier offers opposition to only.
Option
A. holes in the p-region.
Option
B. free electrons in the n-region.
Option
C. majority carriers in both regions.
Correct
Answer is. majority carriers in both regions.
Explanation. NIL. http://en.wikipedia.org/wiki/P-n_junction
Question
Number. 11. Avalanche breakdown occurs when.
Option
A. reverse bias exceeds a certain value.
Option
B. forward bias exceeds a certain value.
Option
C. forward current becomes excessive.
Correct
Answer is. reverse bias exceeds a certain value.
Explanation. Reverse
biasing a diode will cause avalanche breakdown at a certain value.
Aircraft Electricity and Electronics 5th Edition Eismin Page 120.
Question
Number. 12. If forward bias is increased from zero on a p-n junction,
a rapid increase in current flow for a relatively small increase in
voltage occurs.
Option
A. when the flow of minority carriers is sufficient to cause an
avalanche breakdown.
Option
B. when the depletion layer becomes larger than the space charge
area.
Option
C. only after the forward bias exceeds the potential barrier.
Correct
Answer is. only after the forward bias exceeds the potential
barrier.
Explanation. A
forward biased PN junction will conduct only when the forward bias
voltage exceeds the junction barrier - i.e Si = 0.6V, Ge = 0.2V.
Question
Number. 13. A band pass filter excludes frequencies.
Option
A. below the frequency required only.
Option
B. above and below the frequency required.
Option
C. above the frequency required only.
Correct
Answer is. above and below the frequency required.
Explanation. A
band-pass filter excludes frequencies above and below a particular
frequency. Aircraft Electricity and Electronics 5th Edition Eismin
Page 288.
Question
Number. 14. In an unbiased p-n junction, current flow is.
Option
A. zero, because equal but opposite currents are crossing the
junction.
Option
B. zero, because no charges are crossing the junction.
Option
C. due to the diffusion of minority carriers only.
Correct
Answer is. zero, because no charges are crossing the junction.
Explanation. NIL.
Question
Number. 15. With a small amplitude voltage, what type of diode would
you use to produce the output waveform?.
Option
A. Gunn.
Option
B. Zener.
Option
C. Schottky.
Correct
Answer is. Schottky.
Explanation. The
first part of the device is a basic RC differentiator, providing
positive and negative pulses from the square wave input. The diode
blocks the negative pulses. Since the amplitude is small, a fast
acting diode with a low forward bias voltage is required. The
Schottky diode fits the bill.
Question
Number. 16. What diode is used to stop power spikes in a coil?.
Option
A. Gunn diode.
Option
B. Schottky diode.
Option
C. Two directional zener diode.
Correct
Answer is. Two directional zener diode.
Explanation. A
two directional zener diode (actually 2 zener diodes back-to-back) is
used to stop power spikes.
Question
Number. 17. What type of diode when forward biased holes and
electrons recombine producing photons?.
Option
A. LED.
Option
B. Photodiode.
Option
C. Gunn.
Correct
Answer is. LED.
Explanation. The
word 'photons' implies light emission - i.e. a light emitting diode
(LED).
Question
Number. 18. A zener diode is designed to operate.
Option
A. below its breakdown voltage.
Option
B. either above or below its breakdown voltage.
Option
C. above its breakdown voltage.
Correct
Answer is. above its breakdown voltage.
Explanation. A
zener diode is designed to operate above its breakdown voltage
continuously. Aircraft Electricity and Electronics 5th Edition Eismin
Page 120.
Question
Number. 19. A triac is a type of.
Option
A. thermistor.
Option
B. transistor.
Option
C. thyristor.
Correct
Answer is. thyristor.
Explanation. Thyristors
include, SCRs, Triacs and diacs. Aircraft Electricity and Electronics
5th Edition Eismin Page 120.
Question
Number. 20. If a junction diode is reverse biased too far, the output
current would.
Option
A. reverse direction.
Option
B. cease to flow.
Option
C. increase.
Correct
Answer is. increase.
Explanation. If
a junction diode is reverse biased too far, it will 'breakdown' and a
high current will flow.
Question
Number. 21. When a PN junction is forward biased, it conducts via.
Option
A. intrinsic carrier.
Option
B. majority carrier.
Option
C. minority carrier.
Correct
Answer is. majority carrier.
Explanation. Forward
biased - majority carriers.
Question
Number. 22. In the Zener Diode suppressor shown, point X in respect
to point Y should be.
Option
A. more Positive.
Option
B. either positive or negative.
Option
C. more negative.
Correct
Answer is. more negative.
Explanation. A
Zener Diode is always wired in reverse bias. Aircraft Electricity and
Electronics 5th Edition Eismin Page 138.
Question
Number. 23. If the reverse bias voltage across a diode is too high.
Option
A. load current reduces to zero.
Option
B. load current increases rapidly.
Option
C. load current reverses.
Correct
Answer is. load current increases rapidly.
Explanation. If
the reverse bias voltage is too high, the diode will break down and
pass current.
Question
Number. 24. An LED which emits green light uses.
Option
A. gallium phosphide.
Option
B. gallium arsenide.
Option
C. gallium arsenide phosphide.
Correct
Answer is. gallium phosphide.
Explanation. NIL. http://www.oksolar.com/led/led_color_chart.htm
Question
Number. 25. An LED which emits red light uses.
Option
A. gallium phosphide.
Option
B. gallium arsenide phosphide.
Option
C. gallium arsenide.
Correct
Answer is. gallium arsenide phosphide.
Explanation. NIL.
Question
Number. 26. A photodiode is operated under.
Option
A. reverse bias conditions.
Option
B. forward bias conditions.
Option
C. reverse or forward bias conditions.
Correct
Answer is. reverse bias conditions.
Explanation. NIL. http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/photdet.html#c2
Question
Number. 27. To increase capacitance of a varactor diode.
Option
A. reverse bias voltage is increased.
Option
B. reverse bias voltage is decreased.
Option
C. forward bias voltage is decreased.
Correct
Answer is. reverse bias voltage is decreased.
Explanation. NIL. http://www.tpub.com/content/neets/14179/css/14179_131.htm
Question
Number. 28. The diagram shows a.
Option
A. voltage doubler.
Option
B. half wave rectifier.
Option
C. full wave rectifier.
Correct
Answer is. voltage doubler.
Explanation. NIL. http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/voldoub.html
Question
Number. 29. A bi-directional TRIAC has two SCRs connected in.
Option
A. series parallel.
Option
B. inverse parallel.
Option
C. parallel series.
Correct
Answer is. inverse parallel.
Explanation. NIL. http://en.wikipedia.org/wiki/TRIAC
Question
Number. 30. A thyristor can be forward biased by a.
Option
A. positive or negative pulse.
Option
B. negative pulse.
Option
C. positive pulse.
Correct
Answer is. positive pulse.
Explanation. Positive
pulse only.
Question
Number. 31. N' type materials are doped with.
Option
A. acceptors.
Option
B. acceptors and donors.
Option
C. donors.
Correct
Answer is. donors.
Explanation. N'
type materials have excess electrons, therefore the impurity element
is a donor of electrons. Aircraft Electricity and Electronics 5th
Edition Eismin Page 110.
Question
Number. 32. In an electronic circuit, if the anode of a diode is
clamped to ground. What is this called?.
Option
A. A negative clamping circuit.
Option
B. A negative limiting circuit.
Option
C. A positive clamping circuit.
Correct
Answer is. A positive clamping circuit.
Explanation. NIL.
Question
Number. 33. To decrease the capacitance of a varactor.
Option
A. reverse bias should be decreased.
Option
B. forward bias should be increased.
Option
C. reverse bias should be increased.
Correct
Answer is. reverse bias should be increased.
Explanation. NIL.
Question
Number. 34. A Zener diode is used across the output for a power
supply circuit to.
Option
A. give a full wave rectification.
Option
B. prevent thermal runway.
Option
C. provide a steady DC voltage output without falling.
Correct
Answer is. provide a steady DC voltage output without falling.
Explanation. A
Zener diode is the main component in a voltage regulator.
Question
Number. 35. If a diode has gone open circuit in a full wave bridge
rectifier, the output frequency ripple is.
Option
A. the same as the input frequency.
Option
B. twice the input frequency.
Option
C. half the input frequency.
Correct
Answer is. the same as the input frequency.
Explanation. A
fully serviceable bridge rectifier produces an output ripple twice
the input frequency. If one diode goes open circuit, one of the
output 'humps' drops to zero.
Question
Number. 36. In a full wave bridge rectifier.
Option
A. the output is pure DC. Frequency is 0 Hz.
Option
B. the output frequency is twice the input frequency.
Option
C. the output voltage is twice the input voltage.
Correct
Answer is. the output is pure DC. Frequency is 0 Hz.
Explanation. The
output is un-smoothed DC of 2 x input frequency.
Question
Number. 37. After passing through a rectifier, alternating current
becomes.
Option
A. smooth direct current.
Option
B. pulsating direct current.
Option
C. square wave form current.
Correct
Answer is. pulsating direct current.
Explanation. Assuming
the rectifier does not contain any smoothing circuitry.
Question
Number. 38. A Zener diode usually works.
Option
A. only in reverse bias.
Option
B. at variable voltages.
Option
C. only in forward bias.
Correct
Answer is. only in reverse bias.
Explanation. NIL.
Question
Number. 39. P' type materials require.
Option
A. acceptors.
Option
B. conductors.
Option
C. donors.
Correct
Answer is. acceptors.
Explanation. NIL. http://en.wikipedia.org/wiki/P-type_semiconductor
Question
Number. 40. Which of the following explains how the photodiode
works?.
Option
A. Photodiodes are forward biased to conduct when light falls upon
them.
Option
B. Photodiodes are back biased not to conduct when light falls upon
them.
Option
C. Photodiodes are back biased to conduct when light falls upon
them.
Correct
Answer is. Photodiodes are back biased to conduct when light falls
upon them.
Explanation. NIL. http://en.wikipedia.org/wiki/Photodiodes
1.2a.
Semiconductors - Transistors.
Question
Number. 1. In an NPN transistor the P is the.
Option
A. collector.
Option
B. emitter.
Option
C. base.
Correct
Answer is. base.
Explanation. NPN
or PNP, the middle one is always the Base. Aircraft Electricity and
Electronics 5th Edition Eismin Page 116.
Question
Number. 2. When compared to a photo diode, a photo transistor.
Option
A. is less sensitive to light levels.
Option
B. responds faster to changes of light.
Option
C. is slower to respond to changes of light.
Correct
Answer is. is slower to respond to changes of light.
Explanation. NIL.
Question
Number. 3. For correct operation of a transistor, the following
conditions must apply.
Option
A. The base-emitter junction must be forward biased and the
base-collector junction must be greater than 0.7 volts.
Option
B. For an NPN transistor the base-emitter junction must be forward
biased and for a PNP transistor the base emitter junction must be
reverse biased.
Option
C. The base-collector junction must be reverse biased and the
base-emitter junction must be forward biased.
Correct
Answer is. The base-collector junction must be reverse biased and the
base-emitter junction must be forward biased.
Explanation. Eismin
Aircraft Electricity and Electronics 5th Edition page 116.
Question
Number. 4. Current gain in a common emitter amplifier is given the
symbol.
Option
A. Î’.
Option
B. a.
Option
C. Hcg.
Correct
Answer is. Î’.
Explanation. NIL.
Question
Number. 5. When a positive voltage is applied to the base of a
normally biased n-p-n common emitter amplifier.
Option
A. the collector voltage goes less positive.
Option
B. the emitter current decreases.
Option
C. the base current decreases.
Correct
Answer is. the collector voltage goes less positive.
Explanation. Sketch
the circuit and work it out.
Question
Number. 6. Which way does conventional current flow in a PNP
junction?.
Option
A. Emitter to base.
Option
B. Collector to base.
Option
C. Collector to emitter.
Correct
Answer is. Emitter to base.
Explanation. Conventional
current in a PNP transistor flows from EMITTER to BASE. Note: In an
NPN transistor it would be collector to emitter.
Question
Number. 7. For conduction of a transistor, the emitter junction is.
Option
A. forward or reverse as appropriate to the input signal.
Option
B. reverse biased.
Option
C. forward biased.
Correct
Answer is. forward biased.
Explanation. For
a transistor to switch on, the base-emitter (or just emitter)
junction must be forward biased. Aircraft Electricity and Electronics
5th Edition Eismin Page 116.
Question
Number. 8. In a PNP transistor, which way does conventional current
flow?.
Option
A. Base to emitter.
Option
B. Collector to emitter.
Option
C. Emitter to collector.
Correct
Answer is. Emitter to collector.
Explanation. In
a PNP transistor, the main current flow is Emitter to Collector
(reverse of what it is with an NPN transistor).
Question
Number. 9. In a PNP transistor, conventional current will flow
when.
Option
A. the emitter is more positive than the base.
Option
B. the base is more positive than the emitter.
Option
C. the collector is more positive than the emitter.
Correct
Answer is. the emitter is more positive than the base.
Explanation. To
switch a PNP on, the emitter must be positive compared to the base
(opposite to an NPN).
Question
Number. 10. In a common collector circuit the output and input are.
Option
A. in phase.
Option
B. out of phase by 60°.
Option
C. out of phase by 90°.
Correct
Answer is. in phase.
Explanation. Common
collector - output is in-phase with the input.
Question
Number. 11. For an NPN transistor to conduct the collector circuit
has to be.
Option
A. more positive than the base.
Option
B. less positive than the emitter.
Option
C. more positive than the emitter.
Correct
Answer is. more positive than the base.
Explanation. Sketch
an NPN circuit and mark the two current flows. Aircraft Electricity
and Electronics 5th Edition Eismin Page 116.
Question
Number. 12. Point X compared to point.
Option
A. Y is more negative.
Option
B. Z is more positive.
Option
C. Z is more negative.
Correct
Answer is. Z is more positive.
Explanation. NPN
transistor. The collector is more positive than the base. Aircraft
Electricity and Electronics 5th Edition Eismin Page 116/117.
Question
Number. 13. The resistance measured using an AVO between the
Collector and Emitter of a transistor is.
Option
A. smaller Collector to Emitter.
Option
B. same both ways.
Option
C. higher Collector to Emitter.
Correct
Answer is. same both ways.
Explanation. Without
looking too deeply into it, a transistor is two diodes back-to-back,
so have high resistance both ways. Aircraft Electricity and
Electronics 5th Edition Eismin Page 119.
Question
Number. 14. A transistor is used in.
Option
A. current amplifiers.
Option
B. both current amplifiers and voltage amplifiers.
Option
C. voltage amplifiers.
Correct
Answer is. both current amplifiers and voltage amplifiers.
Explanation. A
transistor can amplify either current or voltage or both, depending
on the configuration (CE, CB, CC).
Question
Number. 15. Under normal operating conditions X will be.
Option
A. negative with respect to Z.
Option
B. positive with respect to Z.
Option
C. negative with respect to Y.
Correct
Answer is. positive with respect to Z.
Explanation. The
collector on a NPN transistor is more positive than the base and the
emitter. Aircraft Electricity and Electronics 5th Edition Eismin Page
116/117.
Question
Number. 16. In which direction does the current flow on a PNP
transistor when forward biased?.
Option
A. Emitter to base.
Option
B. Emitter to collector.
Option
C. Collector to emitter.
Correct
Answer is. Emitter to collector.
Explanation. PNP,
current (conventional) flows emitter to collector.
Question
Number. 17. With an NPN transistor electrons leave the.
Option
A. Base.
Option
B. Collector.
Option
C. Emitter.
Correct
Answer is. Emitter.
Explanation. In
a NPN electrons (NOT conventional current) leave at the Emitter.
Question
Number. 18. In a transistor, the arrow always points in the direction
of.
Option
A. electron flow.
Option
B. conventional current.
Option
C. emitter.
Correct
Answer is. conventional current.
Explanation. NIL.
Question
Number. 19. In an NPN transistor the.
Option
A. collector is more positive than the base.
Option
B. collector is the same as the base.
Option
C. emitter is more positive than the base.
Correct
Answer is. collector is more positive than the base.
Explanation. NIL.
Question
Number. 20. In an NPN transistor the.
Option
A. emitter is more positive than the base.
Option
B. collector is more positive than the emitter.
Option
C. emitter is more positive than the collector.
Correct
Answer is. collector is more positive than the emitter.
Explanation. NIL.
1.2b.
Semiconductors - Transistors.
Question
Number. 1. If light entering a photo transistor decreases, the
current to the collector.
Option
A. decreases.
Option
B. remains the same.
Option
C. increases.
Correct
Answer is. decreases.
Explanation. NIL.
Question
Number. 2. A silicon bi-polar transistor with two depletion zones.
Option
A. operates by varying electric fields.
Option
B. is a voltage operated device.
Option
C. consists of 3 slices of semiconductor material.
Correct
Answer is. consists of 3 slices of semiconductor material.
Explanation. NIL.
Question
Number. 3. How is the amplifier in the diagram shown wired?.
Option
A. Common base.
Option
B. Common emitter.
Option
C. Common collector.
Correct
Answer is. Common emitter.
Explanation. NIL.
Question
Number. 4. "To decrease the voltage gain of a common emitter
amplifier you would increase
the
resistance in the."
Option
A. base circuit.
Option
B. emitter circuit.
Option
C. collector circuit.
Correct
Answer is. collector circuit.
Explanation. Decreasing
the collector resistance (RL) increases the output voltage of the
transistor.
Question
Number. 5. The current I/P and O/P waveforms in a common emitter
amplifier are.
Option
A. out of phase.
Option
B. in phase.
Option
C. 90° out of phase.
Correct
Answer is. out of phase.
Explanation. NIL.
Question
Number. 6. Which mode of operation provides the best high frequency
response? Common.
Option
A. emitter.
Option
B. base.
Option
C. collector.
Correct
Answer is. base.
Explanation. NIL.
Question
Number. 7. A FET when compared to a junction transistor is.
Option
A. low impedance.
Option
B. current operated.
Option
C. high impedance.
Correct
Answer is. high impedance.
Explanation. The
biggest advantage of a FET is its high input impedance.
Question
Number. 8. One characteristic of the emitter follower is.
Option
A. low resistance output.
Option
B. low current amplification.
Option
C. high voltage amplification.
Correct
Answer is. low resistance output.
Explanation. The
emitter follower (common collector) has the lowest output resistance
of all three configurations.
Question
Number. 9. An amplifier current gain will be slightly less than 1,
but its voltage gain will be high, if it is connected in the.
Option
A. common base configuration.
Option
B. common emitter configuration.
Option
C. common collector configuration.
Correct
Answer is. common base configuration.
Explanation. Only
the common base configuration provides a current gain of less than
1.
Question
Number. 10. The common collector amplifier is sometimes called the
emitter follower circuit because.
Option
A. the emitter voltage follows the collector voltage.
Option
B. the emitter current follows the collector current.
Option
C. the emitter voltage follows the base voltage.
Correct
Answer is. the emitter voltage follows the base voltage.
Explanation. NIL.
Question
Number. 11. Amplifiers may be classified as.
Option
A. voltage amplifiers or power amplifiers.
Option
B. voltage amplifiers or impedance amplifiers.
Option
C. common emitter or common collector amplifiers.
Correct
Answer is. voltage amplifiers or power amplifiers.
Explanation. Amplifiers
are classified as either voltage or power amplifiers.
Question
Number. 12. An amplifier can provide both voltage gain and current
gain when it is connected in the.
Option
A. common collector configuration.
Option
B. common emitter configuration.
Option
C. common base configuration.
Correct
Answer is. common emitter configuration.
Explanation. Only
the common emitter configuration provides both current and voltage
gain greater than 1.
Question
Number. 13. How do you increase voltage gain of an amplifier?.
Option
A. decrease base circuit bias.
Option
B. decrease input resistance.
Option
C. decrease output resistance.
Correct
Answer is. decrease input resistance.
Explanation. Amplifier
gain = feedback resistance / input resistance.
Question
Number. 14. In the diagram shown, what is resistor R used for?.
Option
A. Amplification.
Option
B. Bias.
Option
C. Stabilisation.
Correct
Answer is. Stabilisation.
Explanation. The
resister R is used to provide thermal stabilisation to the transistor
by supplying negative feedback if the quiescent point moves.
Question
Number. 15. The input and output signals of a common emitter
amplifier are.
Option
A. in phase.
Option
B. equal.
Option
C. out of phase.
Correct
Answer is. out of phase.
Explanation. The
common emitter amplifier is the only configuration which provides an
output which is anti-phase with the input.
Question
Number. 16. A transistor is said to be in the quiescent state when.
Option
A. no currents are flowing.
Option
B. it is unbiased.
Option
C. no signal is applied to the input.
Correct
Answer is. no signal is applied to the input.
Explanation. The
quiescent state of a transistor is when DC is supplied to the base to
bias the transistor. No signal is applied.
Question
Number. 17. A common base transistor circuit is so called because.
Option
A. the base is common to the emitter and collector circuits.
Option
B. the base region is located between the emitter and collector
region.
Option
C. the base is n-type material.
Correct
Answer is. the base is common to the emitter and collector circuits.
Explanation. NIL.
Question
Number. 18. With reference to the circuit shown below, how is the
transistor configured?.
Option
A. Common emitter.
Option
B. Common collector.
Option
C. Common base.
Correct
Answer is. Common emitter.
Explanation. The
diagram shows a common emitter circuit.
Question
Number. 19. In the circuit diagram shown, R1 and R2 are used to.
Option
A. set the transistor gain.
Option
B. increase the base voltage.
Option
C. set the DC bias level.
Correct
Answer is. set the DC bias level.
Explanation. The
resistors R1 and R2 are to set the bias level of the transistor, i.e.
to put the transistor into quiescence.
Question
Number. 20. In a FET, the junction connections are called.
Option
A. drain, source and gate.
Option
B. drain, collector and junctions.
Option
C. base, collector and emitter.
Correct
Answer is. drain, source and gate.
Explanation. The
leads of a FET are called drain, source and gate. Aircraft
Electricity and Electronics 5th Edition Eismin Page 120.
Question
Number. 21. How is a push-pull transistor arrangement connected?.
Option
A. Collector to collector.
Option
B. Emitter to emitter.
Option
C. Base to base.
Correct
Answer is. Emitter to emitter.
Explanation. A
push pull amplifier is wired emitter to emitter.
Question
Number. 22. Thermal runaway in a transistor is caused by.
Option
A. excessive heat causing maximum current flow.
Option
B. excessive heat causing minimum current flow.
Option
C. low heat causing minimum current flow.
Correct
Answer is. excessive heat causing maximum current flow.
Explanation. Thermal
runaway is caused by excessive temperature creating an increase in
current flow and hence an increase in temperature etc. etc..
Question
Number. 23. An advantage of a common emitter is.
Option
A. it has high power gain.
Option
B. it is a voltage follower.
Option
C. it has high voltage gain.
Correct
Answer is. it has high power gain.
Explanation. Common
emitter configuration has a high power gain.
Question
Number. 24. What class of amplifier is biased at cut off?.
Option
A. C.
Option
B. B.
Option
C. A.
Correct
Answer is. B.
Explanation. NIL.
Question
Number. 25. When testing a transistor with an ohmmeter, what is the
resistance of the emitter/collector?.
Option
A. Low resistance both ways.
Option
B. High resistance one way.
Option
C. High resistance both ways.
Correct
Answer is. High resistance both ways.
Explanation. Draw
a transistor as 2 back to back diodes and work it out from there
(same for PNP as NPN). Aircraft Electricity and Electronics 5th
Edition Eismin Page 119.
Question
Number. 26. A transistor at saturation has.
Option
A. low resistance.
Option
B. zero resistance.
Option
C. high resistance.
Correct
Answer is. low resistance.
Explanation. A
transistor at saturation is switched on - therefore has low
resistance.
Question
Number. 27. A capacitor-resistor coupled multistage amplifier lets.
Option
A. DC pass only.
Option
B. AC and DC pass to the next stage.
Option
C. AC pass only.
Correct
Answer is. AC pass only.
Explanation. A
capacitor lets AC pass only.
Question
Number. 28. An oscillator operating at its natural frequency has
feedback which is.
Option
A. 90 degrees out of phase.
Option
B. 180 degrees out of phase.
Option
C. in-phase.
Correct
Answer is. in-phase.
Explanation. An
oscillator provides positive in-phase feedback to switch itself
over.
Question
Number. 29. Which mathematical operation is performed by a modulator
amplifier?.
Option
A. Addition.
Option
B. Subtraction.
Option
C. Multiplication.
Correct
Answer is. Multiplication.
Explanation. A
modulator amplifier is a basic input/output amplifier used for
amplifying a signal. It 'multiplies' the input signal by the value of
the gain.
Question
Number. 30. A JFET is.
Option
A. either of the above depending on resistance in the circuit.
Option
B. current sensitive.
Option
C. voltage sensitive.
Correct
Answer is. voltage sensitive.
Explanation. A
JFET is voltage sensitive, whereas a normal transistor is current
sensitive. Aircraft Electricity and Electronics 5th Edition Eismin
Page 119.
Question
Number. 31. Thermal runaway in a transistor refers to.
Option
A. high current flow when temperature decreases.
Option
B. low current flow when temperature increases.
Option
C. high current flow when temperature increases.
Correct
Answer is. high current flow when temperature increases.
Explanation. Thermal
runaway is caused by the 'negative temperature coefficient' of
semiconductors. More heat, less resistant, hence more current. More
current, more heat etc. etc..
Question
Number. 32. Resistors and capacitors are used to couple stages of
amplifiers so that.
Option
A. only DC can be applied.
Option
B. only AC can be applied.
Option
C. equal amounts of AC and DC can be applied.
Correct
Answer is. only AC can be applied.
Explanation. NIL.
Question
Number. 33. An advantage of a FET when compared to a bi-polar
transistor is.
Option
A. the switching time is quicker.
Option
B. the input resistance is higher.
Option
C. the input resistance is lower.
Correct
Answer is. the input resistance is higher.
Explanation. A
FET has a high input resistance and a low output resistance.
Question
Number. 34. The typical bandwidth for an audio frequency amplifier is
shown by line.
Option
A. Z.
Option
B. X.
Option
C. Y.
Correct
Answer is. X.
Explanation. Audio
frequency is typically 15Hz - 20 kHz, so X is the closest.
Question
Number. 35. Where are decoupling capacitors used in digital
circuits?.
Option
A. Between pins 1 & 8.
Option
B. Close to the positive pin.
Option
C. Close to the negative pin.
Correct
Answer is. Close to the positive pin.
Explanation. Close'
is an important requirement. The capacitor has to be as close as
possible to the +ve power supply pin. Answer a) could also be true
assuming pin 8 to be ground, but in the real world not all pin 8’s
are negative, especially in DIL packages with more than 8 pins.
Question
Number. 36. A Common Collector circuit has the following
characteristics.
Option
A. Medium Voltage Gain, High Current Gain, Non-Inverted Output.
Option
B. Low Voltage Gain, High Current Gain, Inverted Output.
Option
C. Medium Voltage Gain, Low Current Gain, Inverted Output.
Correct
Answer is. Medium Voltage Gain, High Current Gain, Non-Inverted
Output.
Explanation. Common
collector is a voltage follower, with high current gain.
Question
Number. 37. In a Common Emitter Amplifier RE is used for.
Option
A. load control.
Option
B. biasing.
Option
C. stabilisation.
Correct
Answer is. stabilisation.
Explanation. The
emitter resistor is a stabilizing resistor.
Question
Number. 38. In the diagram the relationship of the input to the
output is.
Option
A. 180 degrees out of phase.
Option
B. 90 degrees out of phase.
Option
C. in phase.
Correct
Answer is. 180 degrees out of phase.
Explanation. A
Common Emitter configuration inverts the signal.
Question
Number. 39. The most suitable class of amplifier for a high fidelity
radio transmitter is.
Option
A. B.
Option
B. C.
Option
C. A.
Correct
Answer is. A.
Explanation. Best
amplifier is a Class A.
Question
Number. 40. Which curve is from a Broadband amplifier?.
Option
A. C.
Option
B. A.
Option
C. B.
Correct
Answer is. A.
Explanation. NIL.
Question
Number. 41. A transistor in Common Emitter mode gives.
Option
A. high voltage gain only.
Option
B. high current gain only.
Option
C. high power gain.
Correct
Answer is. high power gain.
Explanation. NIL.
Question
Number. 42. For a transistor in common emitter mode, the term Hfe
indicates.
Option
A. the Voltage gain Vce/Vbe at Ib constant.
Option
B. the Power gain Pin/Pout.
Option
C. the current gain Ic/Ib at Vce constant.
Correct
Answer is. the current gain Ic/Ib at Vce constant.
Explanation. NIL. http://www.vishay.com/brands/measurements_group/guide/glossary/commodvt.htm
Question
Number. 43. In a differential amplifier the term 'common mode
voltage' means.
Option
A. output voltage with one input connected to common ground.
Option
B. output voltage with non-inverting input at 0 volts.
Option
C. output voltage when both inputs have equal voltages.
Correct
Answer is. output voltage when both inputs have equal voltages.
Explanation. NIL.
Question
Number. 44. In an ideal current amplifier.
Option
A. input impedance must be low and output high.
Option
B. input impedance must be high and output low.
Option
C. both input and output impedances must be low.
Correct
Answer is. input impedance must be low and output high.
Explanation. NIL. http://www.safarix.com/0131470469/ch11lev1sec6
Question
Number. 45. In an ideal voltage amplifier.
Option
A. input impedance must be high and output impedance low.
Option
B. input impedance must be low and output impedance high.
Option
C. input impedance must be low and output impedance low.
Correct
Answer is. input impedance must be high and output impedance low.
Explanation. NIL. http://www.safarix.com/0131470469/ch11lev1sec6
Question
Number. 46. The term ICE related to transistor in common emitter mode
means.
Option
A. leakage current flowing between Collector and Emitter with Base
open circuited.
Option
B. forward current between Collector and Emitter with Base connected
to signal.
Option
C. leakage current between Collector and Emitter with Base connected
to ground.
Correct
Answer is. forward current between Collector and Emitter with Base
connected to signal.
Explanation. NIL.
Question
Number. 47. A common base amplifier has.
Option
A. high input and high output impedance.
Option
B. low input and high output impedance.
Option
C. low input and medium output impedance.
Correct
Answer is. low input and high output impedance.
Explanation. NIL. http://www.tpub.com/content/neets/14180/css/14180_48.htm
Question
Number. 48. The emitter, base and collector currents in a common
emitter circuit, follow ohm's and kirchoff's law, which is.
Option
A. Ie = Ic - Ib.
Option
B. Ib = Ie + Ic.
Option
C. Ie = Ib + Ic.
Correct
Answer is. Ie = Ib + Ic.
Explanation. NIL.
1.3a.
Integrated Circuits.
Question
Number. 1. What are the ideal characteristics of an Op Amp?.
Option
A. Infinite gain, infinite input Impedance and infinite output
impedance.
Option
B. Infinite gain, infinite input Impedance and zero output
impedance.
Option
C. Low gain, infinite input Impedance and zero output impedance.
Correct
Answer is. Infinite gain, infinite input Impedance and zero output
impedance.
Explanation. NIL.
Question
Number. 2. What gate does the following Boolean expression represent
F = A.B.C.
Option
A. AND.
Option
B. OR.
Option
C. NOT.
Correct
Answer is. AND.
Explanation. NIL.
Question
Number. 3. What gate does the following Boolean expression represent
F = A+B+C.
Option
A. NOR.
Option
B. OR.
Option
C. NOT.
Correct
Answer is. OR.
Explanation. NIL.
Question
Number. 4. In an integrated circuit, the components are mounted.
Option
A. by metal screws.
Option
B. by metal oxide film.
Option
C. by means of wires connecting them.
Correct
Answer is. by means of wires connecting them.
Explanation. A
thin film of aluminium is coated over the oxide film onto the surface
of the IC to make the conductors.
Question
Number. 5. A non-inverting op-amp.
Option
A. has an inverting input and a non-inverting output.
Option
B. a non-inverting input connection only.
Option
C. has a non-inverting input and an inverting output.
Correct
Answer is. a non-inverting input connection only.
Explanation. NIL.
Question
Number. 6. In an operational amplifier, the two input waves are the
same amplitude, same frequency, but exactly anti-phase. What would
the output be?.
Option
A. Double.
Option
B. Zero.
Option
C. Half.
Correct
Answer is. Double.
Explanation. Although
the input waves are anti-phase, the inverter input of the op amp
inverts one of the inputs, so the two waves actually add to each
other.
Question
Number. 7. In the following Boolean algebra statement, which gate is
described?. F = A + B + C.
Option
A. And.
Option
B. Or.
Option
C. Not.
Correct
Answer is. Or.
Explanation. A+B+C
represents an OR gate.
Question
Number. 8. "In the Boolean algebra statement below, the gate
described is
F
= A.B.C."
Option
A. Nand.
Option
B. And.
Option
C. Nor.
Correct
Answer is. And.
Explanation. A.B.C
represents an AND gate.
Question
Number. 9. Infinite gain, infinite input impedance and zero output
impedance is characteristic of a.
Option
A. Class B amp.
Option
B. Class A amp.
Option
C. Op amp.
Correct
Answer is. Op amp.
Explanation. impedance
and zero output impedance are characteristics of the ideal op amp.
Question
Number. 10. What is meant by a bistable circuit?.
Option
A. The circuit has 2 stable states and will stay in which one it is
put.
Option
B. The circuit has 1 stable state and it can be negative or
positive.
Option
C. The circuit has 2 stable states and will stay in both at the same
time.
Correct
Answer is. The circuit has 2 stable states and will stay in which one
it is put.
Explanation. A
bistable circuit has 2 stable states and it will be in only one at a
time.
Question
Number. 11. What does the output voltage of an op-amp depend upon?.
Option
A. The op amp bandwidth.
Option
B. The gain of the op-amp.
Option
C. The resistors in the circuit.
Correct
Answer is. The resistors in the circuit.
Explanation. The
output of an op-amp is controlled by the external resistor circuit.
Question
Number. 12. What type of gate is an OR gate with both inverted inputs
and inverted outputs?.
Option
A. NAND gate.
Option
B. NOR gate.
Option
C. AND gate.
Correct
Answer is. AND gate.
Explanation. An
AND gate can be made by inverting both the inputs and the output of
an OR gate.
Question
Number. 13. Diodes connected in parallel would act like an.
Option
A. an NAND gate.
Option
B. an AND gate.
Option
C. an OR gate.
Correct
Answer is. an AND gate.
Explanation. NIL.
Question
Number. 14. The output of the circuit shown will be.
Option
A. -15 V.
Option
B. 0 V.
Option
C. +30 V.
Correct
Answer is. 0 V.
Explanation. NIL.
1.3b.
Integrated Circuits.
Question
Number. 1. The voltage supply to a Complimentary Metal Oxide
Semiconductor (CMOS) integrated circuit must be.
Option
A. 0 V is 5 V DC.
Option
B. 3V to 18V DC.
Option
C. 3V to 15V AC.
Correct
Answer is. 3V to 18V DC.
Explanation. NIL.
Question
Number. 2. This is a diagram of a.
Option
A. differentiator.
Option
B. adder.
Option
C. integrator.
Correct
Answer is. differentiator.
Explanation. A
differentiator uses a resistor in the feedback loop across the op
amp.
Question
Number. 2. This is a diagram of a.
Option
A. adder.
Option
B. integrator.
Option
C. differentiator.
Correct
Answer is. differentiator.
Explanation. A
differentiator uses a resistor in the feedback loop across the op
amp.
Question
Number. 3. This is a diagram of a.
Option
A. integrator.
Option
B. adder.
Option
C. differentiator.
Correct
Answer is. integrator.
Explanation. An
integrator has the capacitor in the feedback loop across the op amp.
Question
Number. 4. How are the pins numbered on an op-amp IC?.
Option
A. from left to right from the dot.
Option
B. counter clockwise from the dot.
Option
C. clockwise from the dot.
Correct
Answer is. counter clockwise from the dot.
Explanation. Pins
on an IC are always numbered counter-clockwise from the dot. Aircraft
Electricity and Electronics 5th Edition Eismin Page 140.
Question
Number. 5. On an integrated circuit the hole in the top left corner
is pin 1. The pins are counted.
Option
A. clockwise.
Option
B. from left to right.
Option
C. anticlockwise.
Correct
Answer is. anticlockwise.
Explanation. On
an IC the pins are counted anti-clockwise. Aircraft Electricity and
Electronics 5th Edition Eismin Page 140.
Question
Number. 6. A single integrated circuit Op Amp has how many pins?.
Option
A. 7.
Option
B. 8.
Option
C. 4.
Correct
Answer is. 8.
Explanation. Inverting
and non-inverting input, output, positive and negative supply, two
offset null connections (for a potentiometer) plus one leg not used =
8. Aircraft Electricity and Electronics 5th Edition Eismin Page 140.
Question
Number. 7. What is the output of the amplifier shown?.
Option
A. 5V.
Option
B. 3V.
Option
C. 0V.
Correct
Answer is. 5V.
Explanation. A
basic adding op-amp. 4 + 0 + 1 = 5.
Question
Number. 8. A logic circuit with more than one gate will have.
Option
A. 2 or more outputs.
Option
B. one of 2 states of logic output.
Option
C. an analogue output.
Correct
Answer is. one of 2 states of logic output.
Explanation. Logic
circuit outputs are either 0 or 1, regardless of the number of gates
in the circuit.
Question
Number. 9. Components on an integrated circuit are.
Option
A. on the surface.
Option
B. in the solid.
Option
C. don't need them.
Correct
Answer is. on the surface.
Explanation. Components
on an integrated circuit are on the surface of the substrate.
Question
Number. 10. A VLS IC has.
Option
A. more than 10,000 gates.
Option
B. less than 1000 gates.
Option
C. more than 1000 gates.
Correct
Answer is. more than 10,000 gates.
Explanation. NIL. http://en.wikipedia.org/wiki/Very-large-scale_integration,
http://en.wikipedia.org/wiki/Intergrated_circuit
Question
Number. 11. A momentary input at the reset input of a flip flop
will.
Option
A. reset the true output to 0.
Option
B. clock in new data from the data inputs.
Option
C. reset the true output to 1.
Correct
Answer is. reset the true output to 0.
Explanation. When
the value on reset (R) is 1, the value of Q is set to 0 and vice
versa.
Question
Number. 12. Which type of flip flop has only 1 data input?.
Option
A. JK.
Option
B. D.
Option
C. RS.
Correct
Answer is. D.
Explanation. The
D type Flip Flop has only 1 input (besides the clock input).
Question
Number. 13. When you use an op amp as a buffer it has.
Option
A. low input impedance and high output impedance.
Option
B. high input impedance and low output impedance.
Option
C. the same input an output impedance.
Correct
Answer is. high input impedance and low output impedance.
Explanation. An
op amp is characterised by its high input impedance and low output
impedance. Aircraft Electricity and Electronics 5th Edition Eismin
Page 288.
Question
Number. 14. What is required for the switching of a monostable
multivibrator?.
Option
A. One trigger pulse to both switch on and off.
Option
B. One trigger pulse to switch on and two trigger pulses to switch
off.
Option
C. One trigger pulse to switch on and another to switch off.
Correct
Answer is. One trigger pulse to both switch on and off.
Explanation. Monostable
multivibrators can remain only in one state permanently. When an
external trigger pulse is applied, the circuit moves from its
permanent stable state then drops back after a short while.
Question
Number. 15. An astable multivibrator is a.
Option
A. one which requires no input whatsoever.
Option
B. one which requires an input to switch on and off.
Option
C. free running vibrator.
Correct
Answer is. free running vibrator.
Explanation. An
astable multivibrator flips on/off continuously providing it has a
power supply.
Question
Number. 16. Op amps use what power supply?.
Option
A. 26 VAC.
Option
B. 5-15 VDC.
Option
C. 26 VDC.
Correct
Answer is. 5-15 VDC.
Explanation. Power
supplies vary from op-amp to op-amp (manufacturer to manufacturer)
but most are +/- 5v to +/- 15v.
Question
Number. 17. A device which has a high input impedance, low output
impedance and high voltage gain is a.
Option
A. Op-Amp.
Option
B. Class A amp.
Option
C. Class B amp.
Correct
Answer is. Op-Amp.
Explanation. This
is the definition of an Op-Amp.
Question
Number. 18. In an integrated circuit, the components are mounted
by.
Option
A. a three dimensional process with no connections between them
required.
Option
B. wires connecting them using conformal coating.
Option
C. metal oxide film etched onto the surface.
Correct
Answer is. metal oxide film etched onto the surface.
Explanation. All
three answers are close to the truth. c) is probably the closest.
Aircraft Electricity and Electronics 5th Edition Eismin Page 138.
Question
Number. 19. In an integrated circuit, the components are inserted.
Option
A. automatically.
Option
B. by doping in successive layers.
Option
C. manually.
Correct
Answer is. by doping in successive layers.
Explanation. An
integrated circuit is produced by masking and doping each P and N
component successively. Aircraft Electricity and Electronics 5th
Edition Eismin Page 121.
Question
Number. 20. In an electronic circuit with an operational amplifier
connected in the push-pull configuration, the circuit.
Option
A. utilizes both sides of the input signal.
Option
B. decreases impedance.
Option
C. blocks half of the input signal.
Correct
Answer is. utilizes both sides of the input signal.
Explanation. During
the positive portion of the AC input signal, the NPN follower drives
the output, and during the negative half, the PNP drives the output.
Question
Number. 21. Pin 3 on an op-amp has a + symbol. This designates.
Option
A. positive input DC pin.
Option
B. non-inverting input.
Option
C. positive offset null.
Correct
Answer is. non-inverting input.
Explanation. 741
Op-Amp (for example) is the non-inverting input.
Question
Number. 22. The semiconductor substrate used in 'chips' is most
commonly.
Option
A. silicon.
Option
B. phiidide.
Option
C. germanium.
Correct
Answer is. silicon.
Explanation. Silicon
is most commonly used.
Question
Number. 23. An integrated circuit is manufactured by.
Option
A. doping impurities into layers of intrinsic material.
Option
B. etching copper tracks onto an insulating board.
Option
C. computer hardware, which use individual circuits on ribbon.
Correct
Answer is. doping impurities into layers of intrinsic material.
Explanation. Aircraft
Instruments and Integrated Systems Pallett Page 149/150.
Question
Number. 24. A monostable vibrator.
Option
A. is switched on by a trigger pulse then within a pre-set time will
eventually return to its original state.
Option
B. uses a trigger pulse to turn on and the same pulse to turn off.
Option
C. uses one pulse to turn on and another to turn off.
Correct
Answer is. is switched on by a trigger pulse then within a pre-set
time will eventually return to its original state.
Explanation. A
monostable vibrator is switched on by a trigger pulse then within a
pre-set time will eventually return to its original state.
Question
Number. 25. The negative feedback for an op-amp integrator is
connected across a.
Option
A. resistor.
Option
B. inductor.
Option
C. capacitor.
Correct
Answer is. capacitor.
Explanation. NIL.
Question
Number. 26. The input resistance to an inverting op-amp is 100 Ohms.
The feedback resistance is 100 kilohms. What is the amplifier
gain?.
Option
A. 1000.
Option
B. 1/1000.
Option
C. -1000.
Correct
Answer is. -1000.
Explanation. Gain
= Feedback/input resistance = 100,000/100 = 1000 (minus because it is
inverting).
Question
Number. 27. In an integrated circuit, active, passive and connecting
components are.
Option
A. connected by fine gold wires.
Option
B. mounted on the outside of the solid block.
Option
C. embedded within the solid block.
Correct
Answer is. embedded within the solid block.
Explanation. Hence
the term 'integrated circuit'.
2.
Printed Circuit Boards.
Question
Number. 1. When compared to a system that is constructed on one
board, a modular system using Printed Circuit Boards (PCBs) is.
Option
A. harder to fault find.
Option
B. more expensive for spares.
Option
C. easier to fault find.
Correct
Answer is. easier to fault find.
Explanation. NIL.
Question
Number. 2. A Printed Circuit Board (PCS) is constructed of a plastic
laminate which has bonded to one or both sides.
Option
A. a thin sheet of copper.
Option
B. various thicknesses of copper.
Option
C. a thick sheet of copper.
Correct
Answer is. a thin sheet of copper.
Explanation. NIL.
Question
Number. 3. How is a PCB protected after manufacture?.
Option
A. By conformal coating.
Option
B. With non-conductive varnish.
Option
C. With wax.
Correct
Answer is. By conformal coating.
Explanation. Although
varnish is often used on PCBs, 'conformal coating' is the name of the
process usually applied to aircraft use PCBs. Aircraft Electricity
and Electronics 5th Edition Eismin Page 120.
Question
Number. 4. A multi-layer PCB has.
Option
A. two or more layers on one or both sides.
Option
B. one layer on either side.
Option
C. two or more layers connected in series.
Correct
Answer is. two or more layers on one or both sides.
Explanation. CAIPs
MMC/1-1 Para 15.
Question
Number. 5. When removing a microprocessor.
Option
A. ensure the power is OFF to avoid static discharge.
Option
B. no damage is done by static discharge.
Option
C. considerable damage can be done by static discharge.
Correct
Answer is. considerable damage can be done by static discharge.
Explanation. NIL.
Question
Number. 6. On a PCB, a decoupling capacitor is used to get rid of
transient currents between which points?.
Option
A. The electronic circuit and the aircraft ground.
Option
B. The negative rail and the rest of the circuit.
Option
C. Interspaced along the circuit.
Correct
Answer is. Interspaced along the circuit.
Explanation. The
decoupling capacitor decouples the AC signal from the DC quiescent
current.
Question
Number. 7. A decoupling capacitor in a PCB is used to.
Option
A. minimise transient currents.
Option
B. pass DC only.
Option
C. pass AC only.
Correct
Answer is. pass AC only.
Explanation. A
decoupling capacitor decouples the AC from the DC in a signal, and
blocks the DC.
Question
Number. 8. What is the base material of a PCB?.
Option
A. Insulator.
Option
B. Semiconductor.
Option
C. Conductor.
Correct
Answer is. Insulator.
Explanation. Insulator.
Aircraft Electricity and Electronics 5th Edition Eismin Page 122.
Question
Number. 9. In a printed circuit board , the surface resistance
testing is.
Option
A. insulation resistance between adjacent printed conductor.
Option
B. the resistance between the tow inductors.
Option
C. between the board and the conductor.
Correct
Answer is. insulation resistance between adjacent printed conductor.
Explanation. CAIPs
MMC/1-1 para 4.1.7.
Question
Number. 10. What are printed circuit boards made of?.
Option
A. Fibreglass board coated with copper in which circuits are etched.
Option
B. Synthetic resin board etched with copper.
Option
C. Matrix board with components soldered on.
Correct
Answer is. Fibreglass board coated with copper in which circuits are
etched.
Explanation. NIL.
3a.
Servomechanisms.
Question
Number. 1. The output of a tachogenerator is.
Option
A. proportional to speed of rotation.
Option
B. proportional to position.
Option
C. proportional to acceleration.
Correct
Answer is. proportional to speed of rotation.
Explanation. NIL.
Question
Number. 2. AC power to a synchro system is supplied to.
Option
A. torque transmitter only.
Option
B. both the torque receiver and torque transmitter.
Option
C. torque receiver only.
Correct
Answer is. both the torque receiver and torque transmitter.
Explanation. NIL.
Question
Number. 3. A differential synchro.
Option
A. can be used as either a transmitter or a receiver.
Option
B. can only be used as a receiver.
Option
C. can only be used as a transmitter.
Correct
Answer is. can be used as either a transmitter or a receiver.
Explanation. The
TDX is a transmitter, the TDR is a receiver.
Question
Number. 4. A resolver has.
Option
A. 3 coils on the rotor and 2 coils on the stator.
Option
B. 2 coils on the rotor and 3 coils on the stator.
Option
C. 2 coils on the rotor and 2 coils on the stator.
Correct
Answer is. 2 coils on the rotor and 2 coils on the stator.
Explanation. NIL.
Question
Number. 5. The 'null' point on a control synchro is when the two
rotors are.
Option
A. wired in series.
Option
B. at 90° to each other.
Option
C. parallel to each other.
Correct
Answer is. at 90° to each other.
Explanation. NIL.
Question
Number. 6. The rotor of a desynn indicator is.
Option
A. an electromagnet.
Option
B. a permanent magnet.
Option
C. an AC magnet.
Correct
Answer is. a permanent magnet.
Explanation. NIL.
Question
Number. 7. The position feedback from a potentiometer is.
Option
A. anti-phase.
Option
B. in phase.
Option
C. 90 degrees out of phase.
Correct
Answer is. anti-phase.
Explanation. NIL.
Question
Number. 8. A differential synchro has.
Option
A. single phase stator, 2 phase rotor.
Option
B. 3 phase stator, 3 phase rotor.
Option
C. 3 phase stator, single phase rotor.
Correct
Answer is. 3 phase stator, 3 phase rotor.
Explanation. NIL.
Question
Number. 9. When a servomotor has stopped, the rate feedback from a
tachogenerator is.
Option
A. maximum and in phase.
Option
B. maximum and anti-phase.
Option
C. zero.
Correct
Answer is. zero.
Explanation. NIL.
Question
Number. 10. A tachogenerator is usually used for.
Option
A. angular feedback.
Option
B. rate feedback.
Option
C. position feedback.
Correct
Answer is. rate feedback.
Explanation. NIL.
Question
Number. 11. Differential synchros have.
Option
A. a transmitter and a receiver.
Option
B. a transmitter only.
Option
C. a receiver only.
Correct
Answer is. a transmitter and a receiver.
Explanation. See
Pallett Aircraft Instruments and Integrated Systems pg 135.
Question
Number. 12. In a torque synchro system, the power supply is connected
to.
Option
A. the rotor windings of both the transmitter and receiver.
Option
B. the stator windings of the transmitter.
Option
C. the rotor windings of the transmitter only.
Correct
Answer is. the rotor windings of both the transmitter and receiver.
Explanation. Pallett
Aircraft Instruments and Integrated Systems pg 135. Aircraft
Electricity and Electronics 5th Edition Eismin Page 185/6.
Question
Number. 13. To reduce overshoot errors in a synchro.
Option
A. the gain of the amplifier is increased.
Option
B. the system will have velocity feedback.
Option
C. the system will have position feedback.
Correct
Answer is. the system will have velocity feedback.
Explanation. Velocity
feedback is used to reduce overshoot and oscillations.
Question
Number. 14. A synchro transformer is used to.
Option
A. add the output of two synchro transmitters.
Option
B. derive an error voltage from a synchro transmitter signal and a
shaft position.
Option
C. obtain a 26 volt AC reference.
Correct
Answer is. derive an error voltage from a synchro transmitter signal
and a shaft position.
Explanation. Pallett
Automatic Flight Control pg 135.
Question
Number. 15. Reversal of the complete power to a torque synchro system
will.
Option
A. displace the receiver rotor by 180o.
Option
B. cause reverse rotation of the receiver rotor.
Option
C. have no effect.
Correct
Answer is. have no effect.
Explanation. Since
both rotors are supplied with the same AC, reversing the connections
to both will have no effect.
Question
Number. 16. The power supply to a torque synchro system is.
Option
A. AC or DC.
Option
B. AC.
Option
C. DC.
Correct
Answer is. AC.
Explanation. See
Pallett Aircraft Instruments and Integrated Systems pg 135.
Question
Number. 17. An open loop system is one which has.
Option
A. no direct feedback loop.
Option
B. rate feedback loop.
Option
C. position feedback only.
Correct
Answer is. no direct feedback loop.
Explanation. Open
loop has no feedback.
Question
Number. 18. Mechanical friction in a servo results in.
Option
A. increased inertia.
Option
B. increased damping.
Option
C. reduced gain.
Correct
Answer is. increased damping.
Explanation. Friction
devices are sometimes used to increase damping and thus decrease
oscillations.
Question
Number. 19. The position feedback signal is.
Option
A. phase advanced by 90° with respect to the input signal.
Option
B. in phase with the input demand signal.
Option
C. in anti-phase with the demand signal.
Correct
Answer is. in anti-phase with the demand signal.
Explanation. The
positive feedback must be in anti-phase if it is to oppose the demand
input.
Question
Number. 20. A servo system that overshoots and oscillates is.
Option
A. under damped.
Option
B. over damped.
Option
C. critically damped.
Correct
Answer is. under damped.
Explanation. Oscillations
are caused by an underdamped system.
Question
Number. 21. The power supply to a torque synchro system is connected
to.
Option
A. the transmitter rotor only.
Option
B. the transmitter stator.
Option
C. the transmitter and receiver rotors.
Correct
Answer is. the transmitter and receiver rotors.
Explanation. See
Pallett Aircraft |Instruments and Integrated Systems pg 135.
Question
Number. 22. In a toroidal resistance transmitter indicator system,
the power supply is connected to.
Option
A. the resistor slab.
Option
B. the rotor.
Option
C. the brushes.
Correct
Answer is. the brushes.
Explanation. A
toroidal resistance indicator is better known as a Desynn
indicator.
Question
Number. 23. When a servo has reached its null and stopped, the
velocity feedback is.
Option
A. maximum and anti-phase.
Option
B. maximum and in phase.
Option
C. zero.
Correct
Answer is. zero.
Explanation. Velocity
feedback will stop when the load is at rest.
Question
Number. 24. The primary purpose of rate feedback in a positional
servo system is to.
Option
A. ensure system linearity.
Option
B. prevent excessive overshoot.
Option
C. ensure minimum response time.
Correct
Answer is. prevent excessive overshoot.
Explanation. Rate
feedback is to prevent excessive overshoot and oscillation.
Question
Number. 25. In an AC rate servo, a steady input will result in the
servomotor.
Option
A. rotating to a new datum position.
Option
B. rotating at a constant speed.
Option
C. oscillating about a new datum.
Correct
Answer is. rotating at a constant speed.
Explanation. An
AC rate servo is designed to rotate a load (such as a radar dish) at
a constant speed continually.
Question
Number. 26. In a torque synchro that includes a differential synchro
the power supply is connected to.
Option
A. all three rotors.
Option
B. the transmitter and receiver rotors only.
Option
C. the transmitter rotor only.
Correct
Answer is. the transmitter and receiver rotors only.
Explanation. See
Pallett Aircraft Instruments and Integrated Systems pg 135.
Question
Number. 27. A differential synchro rotor has.
Option
A. three windings.
Option
B. two windings.
Option
C. one winding.
Correct
Answer is. three windings.
Explanation. See
Pallett Aircraft Instruments and Integrated Systems pg 135.
Question
Number. 28. In a resolver synchro the stator windings are
electrically displaced by.
Option
A. 90°.
Option
B. 180°.
Option
C. 120°.
Correct
Answer is. 90°.
Explanation. Pallett
Aircraft Instruments and Integrated Systems pg 135.
Question
Number. 29. A resolver synchro output is obtained from a rotor
with.
Option
A. two coils at 90°.
Option
B. one single coil.
Option
C. three coils at 120°.
Correct
Answer is. two coils at 90°.
Explanation. Pallett
Aircraft Instruments and Integrated Systems pg 135.
Question
Number. 30. In a speed control servo system (rate control), the
purpose of the tachogenerator is.
Option
A. to make the velocity proportional to servo demand.
Option
B. to make the deflection proportional to servo demand.
Option
C. to make it run at constant speed.
Correct
Answer is. to make it run at constant speed.
Explanation. The
tachogenerator is to make the load run at a constant speed.
Question
Number. 31. The rotor of a torque synchro indicator is.
Option
A. supplied with an excitation voltage.
Option
B. connected in series with the transmitter stator coil.
Option
C. short circuited.
Correct
Answer is. supplied with an excitation voltage.
Explanation. The
excitation voltage is that necessary to magnetise the rotor.
Question
Number. 32. To increase the output of a servo amplifier, it is
necessary to.
Option
A. reduce the tacho feedback.
Option
B. increase the position feedback.
Option
C. increase the tacho feedback.
Correct
Answer is. reduce the tacho feedback.
Explanation. Tachogenerator
feedback opposes the error signal and thus reduces amplifier
output.
Question
Number. 33. Angular displacement of the control coils with respect to
the reference coils in a two phase induction motor are.
Option
A. 90°, 270°.
Option
B. 0°, 180°.
Option
C. 90°, 120°.
Correct
Answer is. 90°, 270°.
Explanation. NIL.
Question
Number. 34. A servomotor having only a tachogenerator as a feedback
device will.
Option
A. vary its speed with input error voltage.
Option
B. null out at a position dependant upon input error voltage.
Option
C. have a constant speed for any given input voltage.
Correct
Answer is. have a constant speed for any given input voltage.
Explanation. With
only a tacho feedback it is a rate servo.
Question
Number. 35. The null position of a torque synchro system is when.
Option
A. the TX and TR rotors are parallel to each other.
Option
B. the TX and TR rotors are 90° to each other.
Option
C. the TX and TR rotors are 120° to each other.
Correct
Answer is. the TX and TR rotors are parallel to each other.
Explanation. TX
and TR rotors must be parallel to be at the null position.
Question
Number. 36. An AC tachogenerator stator has.
Option
A. two windings 180° apart.
Option
B. three windings 120° apart.
Option
C. two windings 90° apart.
Correct
Answer is. two windings 90° apart.
Explanation. NIL.
Question
Number. 37. When the rotor of an AC tachogenerator is stationary, the
rotor has.
Option
A. no magnetic fields.
Option
B. no circulating currents.
Option
C. low circulating currents.
Correct
Answer is. low circulating currents.
Explanation. A
small amount of residual voltage exists on the output winding of an
AC tachogenerator when it is stationary.
Question
Number. 38. A closed loop servomechanism.
Option
A. must only have position feedback.
Option
B. must have both position and velocity feedback.
Option
C. can have either position or velocity feedback.
Correct
Answer is. can have either position or velocity feedback.
Explanation. A
closed loop servomechanism can have either position feedback or
velocity feedback or both.
Question
Number. 39. In a control synchro system the power supply is connected
to the.
Option
A. transmitter and receiver rotors.
Option
B. transmitter rotor and amplifier.
Option
C. receiver rotor and amplifier.
Correct
Answer is. transmitter rotor and amplifier.
Explanation. Pallett
Aircraft Instruments and Integrated Systems pg 141.
Question
Number. 40. Velocity feedback.
Option
A. opposes the demand input.
Option
B. assists the demand input.
Option
C. prevents dead space errors.
Correct
Answer is. opposes the demand input.
Explanation. Velocity
feedback is anti-phase to the demand input and opposes it.
Question
Number. 41. An increase in velocity feedback will.
Option
A. decrease the speed the load moves.
Option
B. have no effect on speed.
Option
C. increase the speed the load moves.
Correct
Answer is. decrease the speed the load moves.
Explanation. Velocity
feedback opposes demand input therefore it reduces thew speed the
load moves.
Question
Number. 42. Rate feedback can be obtained from a.
Option
A. tachogenerator.
Option
B. synchro.
Option
C. potentiometer.
Correct
Answer is. tachogenerator.
Explanation. A
tachogenerator produces rate feedback.
Question
Number. 43. Positional feedback can be obtained from a.
Option
A. synchro.
Option
B. potentiometer.
Option
C. tachogenerator.
Correct
Answer is. potentiometer.
Explanation. A
potentiometer produces positional feedback.
Question
Number. 44. The 'null' point in a control synchro is when the two
rotors are.
Option
A. at 90° to each other.
Option
B. wired in series.
Option
C. parallel to each other.
Correct
Answer is. at 90° to each other.
Explanation. In
a control synchro the null position is when the rotors are 90 degrees
to each other (unlike a torque synchro where they must be parallel to
each other).
Question
Number. 45. In a control synchro the stator current ceases to flow
when the.
Option
A. CT rotor is at null.
Option
B. power is removed.
Option
C. two rotors are aligned.
Correct
Answer is. power is removed.
Explanation. In
a control synchro current flows in the stator lines at all times,
regardless of the position of the transformer rotor.
Question
Number. 46. In a rate servo (speed control) the signal into the servo
amplifier is.
Option
A. input voltage plus position feedback voltage.
Option
B. input voltage plus tachogenerator output.
Option
C. input voltage minus tachogenerator output.
Correct
Answer is. input voltage minus tachogenerator output.
Explanation. In
a rate servo the input voltage makes the load rotate and the
tachogenerator output (which is negative feedback) prevents it
rotating too fast.
Question
Number. 47. To reduce oscillations about a demand position.
Option
A. the amount of velocity feedback would be increased.
Option
B. the amount of velocity feedback would be decreased.
Option
C. the amount of position feedback would be increased.
Correct
Answer is. the amount of velocity feedback would be increased.
Explanation. If
velocity feedback is increased, there is more opposition to the
demand signal and the load will move slower and oscillations will be
reduced.
Question
Number. 48. Positive feedback applied to a servomechanism.
Option
A. increases the response of the system.
Option
B. opposes the demand signal.
Option
C. decreases the response of the system.
Correct
Answer is. increases the response of the system.
Explanation. Positive
feedback will add to the input of the amplifier and increase the
response of the system.
Question
Number. 49. A differential synchro rotor consists of.
Option
A. two windings at 90° apart.
Option
B. one winding parallel to the transmitter rotor.
Option
C. three windings at 120° apart.
Correct
Answer is. three windings at 120° apart.
Explanation. Pallett
Aircraft Instruments and Integrated Systems pg 143.
Question
Number. 50. A differential synchro transmitter used for addition
has.
Option
A. the TDX S1 and S3 connections cross connected to the TX.
Option
B. the TDX S1 and S3 connections cross connected to the TR.
Option
C. the TDX R1, R3 and S1, S3 connections cross connected to the TX.
Correct
Answer is. the TDX R1, R3 and S1, S3 connections cross connected to
the TX.
Explanation. To
convert a differential synchro from subtraction to addition you must
swap two of the stator leads AND swap two of the rotor leads at the
differential transmitter.
Question
Number. 51. Differential transmitters are used to.
Option
A. add or subtract two electrical signals.
Option
B. add or subtract a mechanical signal to an electrical synchro
signal.
Option
C. increase the operating speed of the synchro receiver.
Correct
Answer is. add or subtract a mechanical signal to an electrical
synchro signal.
Explanation. A
differential synchro is used to add or subtract a mechanical signal
from an electrical signal derived from the synchro transmitter.
Question
Number. 52. When resolving a Cartesian input to a Polar output.
Option
A. the outputs are two voltages.
Option
B. the inputs are a shaft angle and a voltage.
Option
C. the inputs are two voltages.
Correct
Answer is. the inputs are two voltages.
Explanation. Cartesian
inputs are the X and Y coordinates and are represented by two
voltages. The outputs are represented by a voltage and an angular
position.
Question
Number. 53. A resolver synchro output is obtained from a rotor
with.
Option
A. one single coil.
Option
B. two coils at 90° to each other.
Option
C. three coils at 120° to each other.
Correct
Answer is. two coils at 90° to each other.
Explanation. A
resolver synchro has two coils at 90 degrees to each other.
Question
Number. 54. The output of a resolver synchro is.
Option
A. dependant upon the position of the rotor only.
Option
B. proportional to the speed of input rotation.
Option
C. a function of the rotor position and excitation voltage.
Correct
Answer is. a function of the rotor position and excitation voltage.
Explanation. The
output of a resolver synchro is angular position and a voltage to
represent the distance.
Question
Number. 55. The rotor of an autosyn position indicating system is.
Option
A. a permanent magnet.
Option
B. spring controlled.
Option
C. an electromagnet.
Correct
Answer is. an electromagnet.
Explanation. The
rotor of an autosyn position indicating system is an electromagnet.
Question
Number. 56. The rotor of a magnesyn transmitter is.
Option
A. a permanent magnet.
Option
B. an ac electromagnet.
Option
C. a dc electromagnet.
Correct
Answer is. a permanent magnet.
Explanation. The
rotor of a magnesyn transmitter (and receiver) is a permanent
magnet.
Question
Number. 57. Torque synchro systems are normally used when the.
Option
A. system accuracy is of extreme importance.
Option
B. mechanical load is high.
Option
C. mechanical load is low.
Correct
Answer is. mechanical load is low.
Explanation. Torque
synchros are used for indication only, i.e. when the load is low.
Question
Number. 58. In a resolver synchro the stator windings are
electrically disposed by.
Option
A. 90°.
Option
B. 120°.
Option
C. 180°.
Correct
Answer is. 90°.
Explanation. A
resolver synchro has the windings 90 degrees apart.
Question
Number. 59. Torque synchro systems are normally used when the.
Option
A. system accuracy is of extreme importance.
Option
B. mechanical load is high.
Option
C. mechanical load is low.
Correct
Answer is. mechanical load is low.
Explanation. A
torque synchro is only used for indication - i.e. the load is low.
Question
Number. 60. What device transfers one energy type to another?.
Option
A. Transponder.
Option
B. Transducer.
Option
C. Transmitter.
Correct
Answer is. Transducer.
Explanation. The
device that transfers one energy type to another is called a
transducer. Aircraft Electricity and Electronics 5th Edition Eismin
Page 171.
Question
Number. 61. Electrical power is supplied to a synchro rotor.
Option
A. through slip rings.
Option
B. through a commutator.
Option
C. directly.
Correct
Answer is. through slip rings.
Explanation. Electrical
power is connected to a synchro rotor through slip rings.
Question
Number. 62. In a synchro resolver, the stator coils are at what angle
in relation to one another?.
Option
A. 45 degrees.
Option
B. 80 degrees.
Option
C. 90 degrees.
Correct
Answer is. 90 degrees.
Explanation. In
a synchro resolver the stator coils are 90 degrees to each other."
Question
Number. 63. An increase in negative feedback to the servo
amplifier.
Option
A. has no effect.
Option
B. increases amplifier stability.
Option
C. decreases amplifier stability.
Correct
Answer is. increases amplifier stability.
Explanation. Negative
feedback helps to increase the stability of an amplifier with changes
in temperature and the effects of age.
Question
Number. 64. In a synchro, what is used to convert signals from one
form to another?.
Option
A. Transducer.
Option
B. Transmitter.
Option
C. Transformer.
Correct
Answer is. Transducer.
Explanation. A
'transducer' converts one signal type to another. Aircraft
Electricity and Electronics 5th Edition Eismin Page 171.
Question
Number. 65. A control surface position feedback signal is.
Option
A. inversely proportional to surface position.
Option
B. proportional to surface position.
Option
C. non-linear.
Correct
Answer is. proportional to surface position.
Explanation. Position
feedback is proportional to surface position. Meaning, as control
surface deflection increases, so does the feedback.
Question
Number. 66. A position gyro will provide.
Option
A. acceleration feedback.
Option
B. velocity feedback.
Option
C. positional feedback.
Correct
Answer is. positional feedback.
Explanation. Referring
to a 'position gyro' as in artificial horizon and directional gyro.
Question
Number. 67. In velocity feedback the signal is.
Option
A. out of phase.
Option
B. in phase.
Option
C. equal to the error signal.
Correct
Answer is. out of phase.
Explanation. The
velocity feedback must be anti-phase with the error signal in order
to oppose it (and thus be negative feedback).
Question
Number. 68. If velocity feedback in a servo system is above optimum,
this will cause.
Option
A. no effect.
Option
B. sluggish operation.
Option
C. hunting.
Correct
Answer is. sluggish operation.
Explanation. Velocity
feedback slows down the operation of the rotor.
Question
Number. 69. The amount of rate feedback from a tachogenerator is.
Option
A. proportional to speed.
Option
B. constant for all servo speeds.
Option
C. inversely proportional to speed.
Correct
Answer is. proportional to speed.
Explanation. A
tachogenerator provides feedback proportional to its rate (speed).
Question
Number. 70. What control system is used on an input that gives a
controlled predetermined output?.
Option
A. Control Servo.
Option
B. Closed Loop.
Option
C. Open Loop.
Correct
Answer is. Closed Loop.
Explanation. Only
a closed loop control system can give a predetermined output.
Question
Number. 71. Increasing velocity feedback from optimum will give.
Option
A. faster performance.
Option
B. sluggish performance.
Option
C. no change on the output.
Correct
Answer is. sluggish performance.
Explanation. Velocity
feedback is subtracted from the error signal to reduce the rate of
the output.
Question
Number. 72. A rate control servo system with a steady input voltage
will give.
Option
A. decreasing speed.
Option
B. increasing speed.
Option
C. constant speed.
Correct
Answer is. constant speed.
Explanation. A
rate control system with a steady input voltage will give a constant
speed output.
Question
Number. 73. An increase in amplitude of a rate feedback signal will
cause.
Option
A. sluggish servo operation.
Option
B. unstable operation.
Option
C. reduced hunting.
Correct
Answer is. reduced hunting.
Explanation. Rate
feedback is to reduce overshoot and oscillation (hunting), therefore,
increasing the amplitude (size) of the rate feedback will decrease
tendency to hunt.
Question
Number. 74. An increase in negative feedback.
Option
A. decreases system sensitivity.
Option
B. increases system sensitivity.
Option
C. will make the driven device continuously rotate.
Correct
Answer is. decreases system sensitivity.
Explanation. Negative
feedback (position and/or rate) increases stability but makes the
servo unresponsive to small changes.
Question
Number. 75. Position feedback is used to.
Option
A. indicate to the pilot the position of the load.
Option
B. to prevent control surface oscillations while the surface is being
moved.
Option
C. ensure control surface moves to the demanded position by the
controls.
Correct
Answer is. ensure control surface moves to the demanded position by
the controls.
Explanation. Position
feedback is to ensure control surface moves to (and stops at) the
demanded position by the controls.
Question
Number. 76. The output from a control transformer is.
Option
A. torque.
Option
B. AC voltage.
Option
C. DC voltage.
Correct
Answer is. AC voltage.
Explanation. The
control transformer provides AC voltage in proportion to the error
signal.
Question
Number. 77. The stator output voltages from a synchro resolver are.
Option
A. 3 phase.
Option
B. AC single phase.
Option
C. DC.
Correct
Answer is. AC single phase.
Explanation. AC
single phase from each winding.
Question
Number. 78. A typical use for resolver synchros is.
Option
A. fly by wire system.
Option
B. engine power instrumentation.
Option
C. in compass comparator units.
Correct
Answer is. in compass comparator units.
Explanation. A
resolver synchro converts Cartesian coordinates (grid refs) to polar
(compass reading) and can be used to check the accuracy of the
compass system.
Question
Number. 79. What does a resolver do?.
Option
A. Adds two signals.
Option
B. Resolves a movement into sine and cosine components.
Option
C. Resolves a position into sine and cosine components.
Correct
Answer is. Resolves a position into sine and cosine components.
Explanation. A
resolver converts a position from polar coordinates into cartesian
coordinates, and/or vice versa.
Question
Number. 80. If the feedback is ideally damped, the signal will.
Option
A. overshoots once and return back.
Option
B. not overshoot.
Option
C. oscillate.
Correct
Answer is. overshoots once and return back.
Explanation. NIL.
Question
Number. 81. In a tachogenerator the output voltage is.
Option
A. inversely proportional to the speed.
Option
B. zero.
Option
C. directly proportional to the speed.
Correct
Answer is. directly proportional to the speed.
Explanation. NIL.
Question
Number. 82. The primary purpose of rate feedback in a positional
servo system is to.
Option
A. ensure system linearity.
Option
B. prevent excessive overshoot.
Option
C. ensure minimum response time.
Correct
Answer is. prevent excessive overshoot.
Explanation. NIL.
Question
Number. 83. In a control surface position indicating system the
feedback signal is.
Option
A. in phase with the control surface position.
Option
B. indirectly proportional to the control surface position.
Option
C. proportional to the control surface position.
Correct
Answer is. proportional to the control surface position.
Explanation. NIL.
Question
Number. 84. Synchro systems depend on the principles of.
Option
A. electromagnetic induction.
Option
B. capacitive reaction.
Option
C. mutual Inductance.
Correct
Answer is. mutual Inductance.
Explanation. NIL.
Question
Number. 85. A piezoelectric crystal is an example of.
Option
A. an analogue transducer.
Option
B. a Pneumatic Transducer.
Option
C. a Electro Acoustic Transducer.
Correct
Answer is. an analogue transducer.
Explanation. NIL.
Question
Number. 86. The difference between an open and closed loop is.
Option
A. error signal.
Option
B. feedback.
Option
C. correspondence.
Correct
Answer is. feedback.
Explanation. NIL.
Question
Number. 87. In a Desynn indicator system, where is power supplied
to?.
Option
A. Transmitter and indicator.
Option
B. Indicator only.
Option
C. Transmitter only.
Correct
Answer is. Transmitter only.
Explanation. NIL.
Question
Number. 88. What does the Desynn indicator rotor consist of?.
Option
A. Electro magnet.
Option
B. Permanent Magnet.
Option
C. Aluminium cored coil.
Correct
Answer is. Permanent Magnet.
Explanation. NIL.
3b.
Servomechanisms.
Question
Number. 1. When a servomotor overshoots after a step input and
oscillates it is.
Option
A. under damped.
Option
B. over damped.
Option
C. critically damped.
Correct
Answer is. under damped.
Explanation. NIL.
Question
Number. 2. A reduction from the optimum setting of the velocity
feedback in a servo loop could cause.
Option
A. instability.
Option
B. slow response.
Option
C. ow servo gain.
Correct
Answer is. instability.
Explanation. See
Pallett Automatic Flight Control pg 88.
Question
Number. 3. The phase difference between the supplies of a two phase
induction motor is.
Option
A. 90°.
Option
B. 180°.
Option
C. 0°.
Correct
Answer is. 90°.
Explanation. The
phase difference of the two phases applied to an induction motor is
90°.
Question
Number. 4. If the rotor of the receiver in a torque synchro system
was prevented from aligning with the transmitter rotor, then.
Option
A. the transmitter rotor will turn to align with the receiver rotor.
Option
B. the receiver will hunt.
Option
C. the receiver will overheat.
Correct
Answer is. the receiver will overheat.
Explanation. Current
flows in the stator whenever the rotors are not in correspondence.
Question
Number. 5. An E&I bar output at datum has.
Option
A. an imbalance of voltages in the secondary windings.
Option
B. no induced voltage in the secondary windings.
Option
C. equal and opposite voltages induced in the secondary.
Correct
Answer is. equal and opposite voltages induced in the secondary.
Explanation. See
Pallett Automatic Flight Control pg 130.
Question
Number. 6. The result of cross connecting two of the transmission
leads in a torque synchro system and then turning the rotor of the
transmitter 60° clockwise would be.
Option
A. the receiver would move 60° clockwise.
Option
B. the receiver would move 60° anticlockwise.
Option
C. the receiver would move 120° anticlockwise.
Correct
Answer is. the receiver would move 60° anticlockwise.
Explanation. NIL.
Question
Number. 7. The control windings of a two phase servomotor is supplied
with AC voltage of.
Option
A. variable amplitude, variable phase.
Option
B. variable phase.
Option
C. constant amplitude.
Correct
Answer is. variable amplitude, variable phase.
Explanation. The
control windings are fed with variable amplitude AC but the amplitude
can be positive (in phase) or negative (anti-phase).
Question
Number. 8. If the rotor of a control synchro sticks.
Option
A. the system hunts.
Option
B. the position feedback will oscillate.
Option
C. high current will flow.
Correct
Answer is. high current will flow.
Explanation. High
current flows in the stators whenever the rotors are not in
correspondence.
Question
Number. 9. With the reversal of the connections to the rotor of the
transmitter of a torque synchro, the position of the receiver rotor
will be.
Option
A. changed by 120°.
Option
B. unchanged.
Option
C. changed by 180°.
Correct
Answer is. changed by 180°.
Explanation. NIL.
Question
Number. 10. The application of a 'stick-off' voltage to a control
synchro servo system is.
Option
A. to overcome the effect of static friction.
Option
B. to overcome the effect of viscous friction.
Option
C. to prevent alignment to a false null.
Correct
Answer is. to prevent alignment to a false null.
Explanation. Stick-off
voltage is to prevent alignment to a false null (i.e. 180 degrees
out) when system is switched off.
Question
Number. 11. A servo system may include a brake, an automatic trim
system is one example where a brake is used. The brake is.
Option
A. applied when trimming is complete to prevent stabilizer creep.
Option
B. applied during trimming to prevent oscillations about the demand
position.
Option
C. applied during trimming to prevent servo runaway.
Correct
Answer is. applied when trimming is complete to prevent stabilizer
creep.
Explanation. The
trim switch often consists of 2 separate switches. One is to release
the brake, the other is to switch on the motor.
Question
Number. 12. In a control synchro the stator current ceases to flow
when.
Option
A. the CT rotor is at null.
Option
B. when power is removed.
Option
C. when the two rotors are aligned.
Correct
Answer is. when power is removed.
Explanation. In
a control synchro, the stator is supplied with current at all times,
whatever the transformer rotor position.
Question
Number. 13. The result of reversing the rotor connections to the
receiver of a torque synchro system is that the rotor position.
Option
A. is changed by 180°.
Option
B. is unchanged.
Option
C. is changed by 120°.
Correct
Answer is. is changed by 180°.
Explanation. NIL.
Question
Number. 14. A two phase induction motor used in a servomechanism.
Option
A. will always require a starter.
Option
B. runs with no slip.
Option
C. is self starting under light loads.
Correct
Answer is. is self starting under light loads.
Explanation. NIL.
Question
Number. 15. A hysteresis servo motor is used in a servomechanism
because.
Option
A. it has good starting characteristics.
Option
B. good speed/voltage relationship.
Option
C. low inertia.
Correct
Answer is. it has good starting characteristics.
Explanation. NIL.
Question
Number. 16. Reversal of two of the stator connections on a torque
synchro receiver would cause.
Option
A. the transmitter to become the receiver.
Option
B. the output to move the same direction as the input.
Option
C. the output to move the reverse direction to the input.
Correct
Answer is. the output to move the reverse direction to the input.
Explanation. NIL.
Question
Number. 17. The output of a tachogenerator should be.
Option
A. exponential.
Option
B. linear.
Option
C. sinusoidal.
Correct
Answer is. sinusoidal.
Explanation. The
output should be the same waveform as the input, i.e. sinusoidal.
Question
Number. 18. With a constant input to a speed control servo, the servo
motor.
Option
A. moves to a certain position.
Option
B. moves at a constant speed.
Option
C. oscillates, but otherwise does not move.
Correct
Answer is. moves at a constant speed.
Explanation. A
speed control servo moves the load (e.g. a radar dish) at constant
speed.
Question
Number. 19. Critical damping in a servomechanism is.
Option
A. the point which allows just one overshoot before the load comes to
rest.
Option
B. the amount of damping that results in the load just not
oscillating.
Option
C. the critical damping required for the optimum damping of the
servomechanism.
Correct
Answer is. the amount of damping that results in the load just not
oscillating.
Explanation. damping
results in the fastest time to demand position without any
overshoot.
Question
Number. 20. Reverse rotation of a control transformer rotor can be
caused by.
Option
A. connections to the transmitter rotor reversed.
Option
B. connections between the transformer rotor and the amplifier
reversed.
Option
C. short circuit between two transmission lines.
Correct
Answer is. connections between the transformer rotor and the
amplifier reversed.
Explanation. Reversing
the connections to the amplifier will make the motor run backwards.
Then the feedback will drive the transformer rotor in the wrong
direction.
Question
Number. 21. Velocity lag can be decreased by.
Option
A. keeping the error detector (summing point) output as low as
possible.
Option
B. introduction of an integrator.
Option
C. decreasing the coulomb friction in the system.
Correct
Answer is. decreasing the coulomb friction in the system.
Explanation. Coulomb
friction is one of the things which causes velocity lag.
Question
Number. 22. A two phase motor will stop when.
Option
A. the control phase is reversed.
Option
B. the reference phase is reversed.
Option
C. the control phase is zero.
Correct
Answer is. the control phase is zero.
Explanation. A
two phase motor will stop when the control phase is zero (i.e. no
output).
Question
Number. 23. A tachogenerator output is.
Option
A. variable frequency, constant voltage.
Option
B. variable frequency, variable voltage.
Option
C. variable voltage, constant frequency.
Correct
Answer is. variable voltage, constant frequency.
Explanation. A
tachogenerator output is the same frequency as the input (i.e.
constant) but the voltage varies.
Question
Number. 24. If two of the stator leads are cross connected in a
control synchro system, a 25° clockwise rotation of the input rotor
would result in the output rotor.
Option
A. moving 180° to rectify the defect.
Option
B. moving 25° anticlockwise.
Option
C. moving 25° clockwise.
Correct
Answer is. moving 25° anticlockwise.
Explanation. Cross
connecting two stator leads of a control synchro will make the
magnetic field in the receiver rotate in the opposite direction as
the transmitter.
Question
Number. 25. Damping in a servomechanism is easier to apply if.
Option
A. the mechanism is light and has high inertia.
Option
B. the mechanism is light and has low inertia.
Option
C. the mechanism is heavy and has high inertia.
Correct
Answer is. the mechanism is light and has low inertia.
Explanation. Overshoot
and oscillation is greatest when the mechanism is heavy and has a
high inertia.
Question
Number. 26. If the electrical connections to the feedback generator
in a control synchro system were disconnected, the.
Option
A. motor would run in the wrong direction.
Option
B. input signal to the amplifier would reduce.
Option
C. system would tend to oscillate.
Correct
Answer is. system would tend to oscillate.
Explanation. Feedback
from the tachogenerator prevents overspeed and overshoot, so
disconnecting the feedback will cause the load to overshoot and
oscillate.
Question
Number. 27. An increase in servo amplifier gain.
Option
A. increases system response.
Option
B. reduces tendency to hunt.
Option
C. reduces the speed of the system.
Correct
Answer is. increases system response.
Explanation. Increasing
servo-amplifier gain will make the system respond faster but will
also cause it to overshoot and oscillate (hunt).
Question
Number. 28. The term 'velocity lag' refers to a.
Option
A. speed error.
Option
B. acceleration error.
Option
C. position error.
Correct
Answer is. position error.
Explanation. Velocity
lag is the difference between the demand input and the load position.
It is therefore a position error.
Question
Number. 29. The rotor of an AC tachogenerator.
Option
A. rotates at constant speed.
Option
B. has skewed slots.
Option
C. has a copper, brass or aluminium cylinder.
Correct
Answer is. has a copper, brass or aluminium cylinder.
Explanation. An
AC generator rotor is made from a diamagnetic material such as
copper, brass or aluminium.
Question
Number. 30. A servo system with transient negative velocity
feedback.
Option
A. is damped with little velocity lag.
Option
B. is underdamped with high velocity lag.
Option
C. is damped with high velocity lag.
Correct
Answer is. is damped with little velocity lag.
Explanation. Transient
velocity feedback is a variable feedback which can be switched on
when the system is about to overshoot (and anticipates the
overshoot). But it can also be switched off when it is not required
to reduce the velocity lag.
Question
Number. 31. To reverse the direction of rotation of a two phase
induction motor.
Option
A. reverse the polarity of both the control phase and reference
phase.
Option
B. reverse the polarity of the control phase.
Option
C. shift the reference by 90°.
Correct
Answer is. reverse the polarity of the control phase.
Explanation. To
reverse the direction of a two phase induction motor the control
phase must be out of phase with the reference phase.
Question
Number. 32. Loss of DC to a servo amplifier causes the motor to.
Option
A. reverse.
Option
B. stop.
Option
C. run continuously.
Correct
Answer is. stop.
Explanation. Loss
of DC to the servo-amplifier will cause the amplifier to stop working
and the motor will therefore stop running.
Question
Number. 33. An AC servo demand can be converted to drive a DC motor
by the introduction of a.
Option
A. rectifier.
Option
B. demodulator.
Option
C. modulator.
Correct
Answer is. demodulator.
Explanation. A
demodulator differs from a rectifier in that it can sense the phase
of the AC input, and give an output either positive DC or negative DC
accordingly. This then drives the DC motor in the correct
direction.
Question
Number. 34. Synchro indicator systems are used when the indication is
required to move.
Option
A. a fraction of the input distance.
Option
B. at the same rate as the input.
Option
C. slower than the input rate.
Correct
Answer is. at the same rate as the input.
Explanation. A
synchro indicator moves at the same speed as the input.
Question
Number. 35. A linear variable differential transformer is used to
measure position feedback where.
Option
A. an output whose phase is related to direction of movement and
amplitude linear over a wide range.
Option
B. 360° of rotation and high angular accuracy is required.
Option
C. is of limited importance but robust construction and reliability
is important.
Correct
Answer is. an output whose phase is related to direction of movement
and amplitude linear over a wide range.
Explanation. An
LVDT measures position and provides a different phase according to
the direction of movement.
Question
Number. 36. A low frequency sinusoidal input will cause a closed loop
servomechanism load to.
Option
A. move backwards and forwards at the input frequency.
Option
B. move backwards and forwards at the input frequency.
Option
C. move to a demand position with no overshoot.
Correct
Answer is. move to a demand position with no overshoot.
Explanation. A
closed loop servo mechanism (whatever frequency) will move to the
demand position with no or minimal overshoot.
Question
Number. 37. If a servo amplifier is suffering from drift.
Option
A. the load would move to a new position, proportional to the drift
and then return back to the datum position.
Option
B. the load would move to a new position, proportional to the drift
and stay there.
Option
C. the load would oscillate about the datum position.
Correct
Answer is. the load would move to a new position, proportional to the
drift and stay there.
Explanation. If
a servo amplifier suffers from drift (e.g. due to age or
temperature), the load will move to a new position and stop when the
position feedback cancels out the drift signal.
Question
Number. 38. In a transient velocity feedback circuit, the
tachogenerator output is summated with the demand voltage.
Option
A. at all times when the load is moving.
Option
B. only when the load is speeding up or slowing down.
Option
C. only when the load is slowing down.
Correct
Answer is. only when the load is speeding up or slowing down.
Explanation. Automatic
Flight Control EHJ Pallett Page 91.
Question
Number. 39. An LVDT has.
Option
A. an output winding which is wound in series opposition.
Option
B. an input winding whose voltage will change with load movement.
Option
C. an output winding whose voltage and frequency is linear to load
angular movement.
Correct
Answer is. an output winding which is wound in series opposition.
Explanation. An
LVDT has an output winding which is wound in series opposition.
Question
Number. 40. To convert a differential synchro from subtraction to
addition you would.
Option
A. change over two rotor and two stator connections.
Option
B. change over all three stator windings.
Option
C. reverse the reference phase supply.
Correct
Answer is. change over two rotor and two stator connections.
Explanation. To
convert a differential synchro from subtraction to addition you must
swap two of the rotor leads AND swap two of the stator leads.
Question
Number. 41. In general the accuracy of a synchro system increases if
the.
Option
A. stator current is low.
Option
B. rotor current is high.
Option
C. stator current is high.
Correct
Answer is. stator current is low.
Explanation. The
synchro system is only accurate when the two rotors are in
correspondence. At this time the stator current is zero.
Question
Number. 42. The induced signal in the output coils of the magnesyn
system.
Option
A. de-saturates the soft iron core.
Option
B. is of a value of 800 Hz.
Option
C. damps the pointer oscillations.
Correct
Answer is. is of a value of 800 Hz.
Explanation. A
signal from the permanent magnet flux is induced every time the soft
iron comes out of saturation. Therefore, if the supply is 400 Hz the
induced signal is 800 Hz.
Question
Number. 43. The direction of the induced (secondary) magnetic field
in a synchro transmitter.
Option
A. in the same direction as the primary field.
Option
B. is in the opposite direction to the primary field.
Option
C. is 90° to the primary magnetic field.
Correct
Answer is. is in the opposite direction to the primary field.
Explanation. The
rotor of a synchro transmitter induces a current into the stator
coils. The stator coils produce a magnetic field which opposes the
field in the rotor which created it. (Similar to the secondary field
of a transformer).
Question
Number. 44. The cogging effect in synchros is rectified by.
Option
A. using an elliptical cog.
Option
B. skewing the rotor.
Option
C. using carbon brushes.
Correct
Answer is. skewing the rotor.
Explanation. The
cogging effect in a synchro is prevented by skewing (or twisting) the
rotor.
Question
Number. 45. Reversal of the power supply to either the transmitter or
the receiver of a torque synchro system would.
Option
A. make the receiver rotor rotate in the opposite direction.
Option
B. cause a 180° displacement between the transmitter and the
receiver.
Option
C. have no effect on the indication, but would cause a heavy current
to flow.
Correct
Answer is. cause a 180° displacement between the transmitter and the
receiver.
Explanation. Reversal
of the power supply to either the transmitter or the receiver will
cause a 180 degree displacement of the receiver rotor.
Question
Number. 46. The purpose of a flywheel incorporated in a synchro is
to.
Option
A. increase the driving force.
Option
B. prevent insect ingress.
Option
C. prevent oscillations.
Correct
Answer is. prevent oscillations.
Explanation. The
purpose of a flywheel on a synchro is as part of a eddy current
(coulomb friction) damping mechanism.
Question
Number. 47. In a synchro system, if two stator lines are crossed the
receiver will.
Option
A. be 180° out.
Option
B. not be affected.
Option
C. reverse direction.
Correct
Answer is. reverse direction.
Explanation. If
two stator lines are crossed the receiver will reverse in
direction.
Question
Number. 48. In an E and I signal generator at datum, the voltage on
the secondary windings.
Option
A. is zero.
Option
B. is maximum.
Option
C. are equal and opposite.
Correct
Answer is. are equal and opposite.
Explanation. Since
an EandI bar transformer secondary winding is wound in series
opposition, at datum the voltage in the secondary windings will be
equal and opposite and cancel.
Question
Number. 49. In a synchrotel, the.
Option
A. stator coil is fixed and the rotor coil moves.
Option
B. rotor coil and stator coil is fixed.
Option
C. rotor coil is fixed and the stator coil moves.
Correct
Answer is. rotor coil and stator coil is fixed.
Explanation. Aircraft
Instruments and Integrated Systems Pallett Page 149/150.
Question
Number. 50. An E&I transformer out of datum has.
Option
A. equal and opposite voltages in each windings.
Option
B. unequal and opposite voltages in both windings.
Option
C. no voltage in either winding.
Correct
Answer is. unequal and opposite voltages in both windings.
Explanation. Off
datum, the E&I transformer has unequal and opposite voltages in
the windings (and hence an output).
Question
Number. 51. When is maximum voltage induced into the rotor of a
control synchro transformer?.
Option
A. 90 degrees (null position).
Option
B. 0 degrees.
Option
C. When spinning fast.
Correct
Answer is. 0 degrees.
Explanation. NIL.
Question
Number. 52. To check the output of a synchro stator it would be
preferable to use.
Option
A. a Valve Voltmeter.
Option
B. a Cambridge Bridge.
Option
C. an Avometer.
Correct
Answer is. a Valve Voltmeter.
Explanation. Since
the synchro stator output is a very low voltage, a high impedance
multimeter would be used. Since this is not an answer provided the
most sensitive of the three is the Valve Voltmeter.
Question
Number. 53. Synchro capacitors are connected into synchro systems
to.
Option
A. act as spark suppression due to wear of the slip rings.
Option
B. increase the accuracy of the control synchro.
Option
C. minimize the torque synchro stator current at null.
Correct
Answer is. increase the accuracy of the control synchro.
Explanation. Synchro
capacitors increase the accuracy of the synchro system.
Question
Number. 54. In a slab desynn transmitter the.
Option
A. pick-offs form part of the circuit resistance.
Option
B. pick-offs rotate on the slab resister.
Option
C. pick-offs are connected to a spark suppressor.
Correct
Answer is. pick-offs rotate on the slab resister.
Explanation. The
pick-offs rotate on the slab resistor. Aircraft Electricity and
Electronics 5th Edition Eismin Page 352.
Question
Number. 55. If, in a servo system, the amplitude from the feedback
system is below normal, the servo will.
Option
A. be sluggish in operation.
Option
B. oscillate.
Option
C. be overdamped.
Correct
Answer is. oscillate.
Explanation. The
feedback system is designed to prevent overshoot and oscillation
(hunting).
Question
Number. 56. A desynn instrument has a positive regular increasing
error, you would adjust.
Option
A. lever length.
Option
B. lever angle and lever length.
Option
C. lever angle.
Correct
Answer is. lever angle.
Explanation. NIL.
Question
Number. 57. Torque synchro receiver bearing friction will cause.
Option
A. improved accuracy.
Option
B. misalignment.
Option
C. hunting.
Correct
Answer is. misalignment.
Explanation. Bearing
friction will cause the delicate rotor to stop before the desired
position.
Question
Number. 58. A control synchro system pointer is.
Option
A. actuated by a permanent magnet.
Option
B. displaced by the torque of the stator.
Option
C. motor driven.
Correct
Answer is. motor driven.
Explanation. The
receiver of a control synchro is effectively a slow speed synchronous
motor.
Question
Number. 59. A D.C. signal converted to a phase sensitive A.C. is.
Option
A. modulation.
Option
B. demodulation.
Option
C. phase conversion.
Correct
Answer is. modulation.
Explanation. DC
to phase sensitive AC = 'modulation'.
Question
Number. 60. The rotor coil of a synchrotel.
Option
A. rotates only when a current flows in it.
Option
B. rotates.
Option
C. is stationary.
Correct
Answer is. is stationary.
Explanation. NIL.
Question
Number. 61. The purpose of synchro capacitors in a differential
synchro transmission system.
Option
A. reduce stator circuit impedance.
Option
B. to reduce stator current.
Option
C. reduce rotor current.
Correct
Answer is. to reduce stator current.
Explanation. Synchro
capacitors reduce stator current and make the synchro system more
accurate.
Question
Number. 62. The purpose of a flywheel in a synchro receiver indicator
is to.
Option
A. increase driving torque.
Option
B. prevent spinning or oscillation.
Option
C. encourage spinning.
Correct
Answer is. prevent spinning or oscillation.
Explanation. The
flywheel is coupled to some form of brake (e.g. magnetic) to reduce
oscillations.
Question
Number. 63. A linear variometer is.
Option
A. a special synchro giving ac output proportional to shaft angle.
Option
B. a special auto transformer for synchro system power supplies.
Option
C. an alternative term for a desynn system.
Correct
Answer is. a special synchro giving ac output proportional to shaft
angle.
Explanation. A
linear variometer is a device which gives an output voltage directly
proportional to angle when coupled to a gyro (for example).
Question
Number. 64. In a synchrotel the rotating winding is.
Option
A. the stator.
Option
B. rotor.
Option
C. neither.
Correct
Answer is. neither.
Explanation. This
is a trick question, because a synchrotel has NO rotating winding.
Aircraft Instruments and Integrated Systems Pallett Page 149/150.
Question
Number. 65. The receiver rotor in a torque synchro system oscillates
over an arc of approx 75 degrees. The probable cause is.
Option
A. one stator line open circuit.
Option
B. two stator lines reversed.
Option
C. short circuit between two stator lines.
Correct
Answer is. one stator line open circuit.
Explanation. A
'possible' symptom of a stator line open.
Question
Number. 66. Synchro capacitors are fitted.
Option
A. to improve sensitivity and accuracy.
Option
B. to provide critical damping.
Option
C. to make additional damping features unnecessary.
Correct
Answer is. to improve sensitivity and accuracy.
Explanation. Synchro
capacitors reduce stator current and make the synchro system more
accurate.
Question
Number. 67. The output of a control transformer is made.
Option
A. phase and amplitude sensitive by direction and magnitude of the
transmitter rotor movement respectively.
Option
B. phase and amplitude sensitive by magnitude and direction of the
transmitter rotor movement respectively.
Option
C. phase sensitive by transmitter rotor excitation and amplitude
sensitive by direction of transmitter rotor movement.
Correct
Answer is. phase and amplitude sensitive by direction and magnitude
of the transmitter rotor movement respectively.
Explanation. Phase
provided by TX rotor direction, amplitude provided by TX rotor
displacement (magnitude).
Question
Number. 68. The letter 'B' following the identification code on the
case of a synchro denotes.
Option
A. that the synchro is second hand.
Option
B. the modification status.
Option
C. that the stator is rotatable.
Correct
Answer is. that the stator is rotatable.
Explanation. NIL. http://www.tpub.com/content/neets/14187/css/14187_18.htm
Question
Number. 69. TX is the abbreviation for a.
Option
A. torque transmitter.
Option
B. control transformer.
Option
C. torque receiver.
Correct
Answer is. torque transmitter.
Explanation. NIL.
Question
Number. 70. TR is the abbreviation for a.
Option
A. transmitter Resolver.
Option
B. torque receiver.
Option
C. torque synchro.
Correct
Answer is. torque receiver.
Explanation. NIL.
Question
Number. 71. When a synchro system is in correspondence, its
transmitter and receiver.
Option
A. are in phase.
Option
B. are anti-phase.
Option
C. are at 90° to each other.
Correct
Answer is. are in phase.
Explanation. NIL.
4.
Question
Number. 1. The reference phase to a synchro is.
Option
A. 50 Hz.
Option
B. 28 VDC.
Option
C. 400 Hz.
Correct
Answer is. 400 Hz.
Explanation. Aircraft
Electricity and Electronics, TK Eismin Page 353.
Question
Number. 2. In rate feedback, when the motor has reached the commanded
position, the output will be.
Option
A. maximum and in-phase with the input.
Option
B. maximum and out-of-phase with the input.
Option
C. zero.
Correct
Answer is. zero.
Explanation. Assuming
it is a position servo, not a rate servo (but all three answers are
incorrect if it is a rate servo).
Question
Number. 3. What power is required for a desynn indicator system?.
Option
A. DC.
Option
B. AC 400 Hz.
Option
C. AC 50 Hz.
Correct
Answer is. DC.
Explanation. NIL.
Question
Number. 4. What material would have 3 electrons in the outermost
orbit?.
Option
A. Majority Carrier material.
Option
B. The donor to an N-Type semi-conductor material.
Option
C. The acceptor to a P-Type semi-conductor material.
Correct
Answer is. The acceptor to a P-Type semi-conductor material.
Explanation. NIL.
Question
Number. 5. a microprocessor on a PCB.
Option
A. is not easily damaged by static-electricity.
Option
B. is easily damaged by static-electricity if mishandling.
Option
C. is only easily damaged by static-electricity if removed from teh
PCB.
Correct
Answer is. is easily damaged by static-electricity if mishandling.
Explanation. NIL.
Question
Number. 6. On a torque synchro, the AC power supply is applied to.
Option
A. the rotors of both the transmitter and the receiver.
Option
B. the rotor of the transmitter only.
Option
C. the stators of both the transmitter and the receiver.
Correct
Answer is. the rotors of both the transmitter and the receiver.
Explanation. NIL.
Question
Number. 7. The Characteristic Curve of a transistor is plotted on
axis of.
Option
A. base current against Vec.
Option
B. collector current against Vbe.
Option
C. collector current against Vec.
Correct
Answer is. collector current against Vec.
Explanation. NIL. http://www.st-andrews.ac.uk/~jcgl/Scots_Guide/info/comp/active/BiPolar/bpcur.html
Question
Number. 8. Amplifier output characteristics are defined by.
Option
A. the collector resistance.
Option
B. the effect of the load resistor.
Option
C. the configuration of the transistor.
Correct
Answer is. the configuration of the transistor.
Explanation. NIL.
Question
Number. 9. What Type of Diode is this?.
Option
A. Varactor Diode.
Option
B. Double Acting Diode.
Option
C. Shottky Diode.
Correct
Answer is. Shottky Diode.
Explanation. NIL. http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/varactor.html
Question
Number. 10. A device which provides cheap and convenient variable
power supply is a.
Option
A. Diac.
Option
B. Variac.
Option
C. Triac.
Correct
Answer is. Variac.
Explanation. NIL. http://en.wikipedia.org/wiki/Autotransformer
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