Part 66 Electronic

This is exam number 1. You've been here 1 times.

1 What gives the colour of an LED?

a) The plastic it is encased in

b) The active element

c) The type of gas used inside it

The correct answer is b The active element is the element used in the doping of the semiconductor material. Aircraft Electricity and Electronics 5th Edition Eismin Page 121

2 A germanium diode is used for

a) rectification

b) voltage stabilization

c) modulation

The correct answer is a Germanium diode has the least forward bias voltage drop and is best for recification

3 Why is a diode put in parallel with an LED?

a) To protect it from AC

b) So it will work only above a certain voltage

c) So it will work only below a certain voltage

The correct answer is a An LED has a high forward bias voltage drop but is easily damaged when reverse biased. AC is therefore not good for an LED

4 When testing the forward bias of a diode with a multimeter

a) the positive lead of the ohmeter is placed on the cathode

b) the positive lead of the ohmeter is placed on the anode

c) it does not matter which terminal the positive lead of the ohmeter is placed

The correct answer is b 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

5 In an NPN transistor the P is the

a) collector

b) base

c) emitter

The correct answer is b NPN or PNP, the middle one is always the Base. Aircraft Electricity and Electronics 5th Edition Eismin Page 116

6 The output of a tachogenerator is

a) proportional to speed of rotation

b) proportional to position

c) proportional to acceleration

The correct answer is a Read up on tachogenerators

7 AC power is supplied to

a) torque receiver only

b) torque transmitter only

c) both the torque receiver and torque transmitter

The correct answer is c Read up on torque synchros

8 This is a diagram of

a) a TRIAC

b) an SCR

c) a Schottky diode

The correct answer is b You just have to know the different types of semiconductor applications

9 How is a PCB protected after manufacture?

a) With non-conductive varnish

b) With wax

c) By conformal coating

The correct answer is c 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

10 A differential synchro

a) can only be used as a transmitter

b) can only be used as a receiver

c) can be used as either a transmitter or a receiver

The correct answer is c The TDX is a transmitter, the TDR is a receiver.


1 Which of the following describes the characteristics of a Thyristor?

a) High voltage handling

b) High current handling

c) High power handling

The correct answer is b A thyristor (such as an SCR) is a high current switching device

2 A semiconductor doped with an element having a valency of 5 will produce

a) an N type material

b) a P type material

c) either an N type or a P type depending on what type of semiconductor material is used

The correct answer is a Pentavalent materials make an N type material due to its extra electron. Aircraft Electricity and Electronics 5th Edition Eismin Page 110

3 What are the ideal characteristics of an Op Amp?

a) Infinite gain, infinite input Impedance and infinite output impedance

b) Low gain, infinite input Impedance and zero output impedance

c) Infinite gain, infinite input Impedance and zero output impedance

The correct answer is c Read up on Op Amps

4 How is the amplifier in the diagram shown wired?

a) Common base

b) Common emitter

c) Common collector

The correct answer is b Learn all the amplifier configurations

5 What gate does the following Boolean expression represent

F = A.B.C

a) AND

b) OR

c) NOT

The correct answer is a You must know the Boolean expressions

6 What gate does the following Boolean expression represent

F = A+B+C

a) NOT

b) NOR

c) OR

The correct answer is c You must know the Boolean expressions

7 To decrease the voltage gain of a common emitter amplifier you would increase the resistance in the

a) base circuit

b) collector circuit

c) emitter circuit

The correct answer is b Decreasing the collector resistance (RL) increases the output voltage of the transistor.

8 A resolver has

a) 2 coils on the rotor and 2 coils on the stator

b) 3 coils on the rotor and 2 coils on the stator

c) 2 coils on the rotor and 3 coils on the stator

The correct answer is a Read up on resolvers

9 The 'null' point on a control synchro is when the two rotors are

a) at 90o to each other

b) parallel to each other

c) wired in series

The correct answer is a Read up on synchros

10 A FET when compared to a junction transistor is

a) low impedance

b) high impedance

c) current operated

The correct answer is b The biggest advantage of a FET is its high input impedence


1 What type of diode would be used to stop voltage spikes across a coil of a relay?

a) Gunn diode

b) Schottky diode

c) Double acting diode

The correct answer is c Read up on the different types of diode. Aircraft Electricity and Electronics 5th Edition Eismin Page 121

2 A silicon diode, when compared to a germanium diode has

a) a higher forward bias voltage

b) less forward bias voltage

c) the same forward bias voltage

The correct answer is a Si = 0.6V, Ge = 0.2V. Aircraft Electricity and Electronics 5th Edition Eismin Page 111

3 A zener diode is used for

a) rectification

b) voltage stabilization

c) modulation

The correct answer is b Read up on the different types of diode

4 A multi-layer PCB has

a) one layer on either side

b) two or more layers on one or both sides

c) two or more layers connected in series

The correct answer is b CAIPs MMC/1-1 Para 15.

5 When a servomotor overshoots after a step input and oscillates it is

a) over damped

b) under damped

c) critically damped

The correct answer is b Get a copy of Pallett's Automatic Flight Control and read up on servos

6 The rotor of a desynn indicator is

a) an electromagnet

b) a permanent magnet

c) an AC magnet

The correct answer is b Read up on Desynn system. Aircraft Electricity and Electronics 5th Edition Eismin Page 352

7 The position feedback from a potentiometer is

a) anti-phase

b) in phase

c) 90 degrees out of phase

The correct answer is a Get a copy of Pallett's Automatic Flight Control and read up on servos

8 A differential synchro has

a) 3 phase stator, 3 phase rotor

b) single phase stator, 2 phase rotor

c) 3 phase stator, single phase rotor

The correct answer is a Get a copy of Pallett's Automatic Flight Control and read up on synchros

9 When a servomotor has stopped, the rate feedback from a tachogenerator is

a) zero

b) maximum and in phase

c) maximum and anti-phase


10 A tachogenerator is usually used for

a) rate feedback

b) angular feedback

c) position feedback



1 What is this circuit?

a) Half wave rectifier

b) Full wave rectifier

c) Flywheel diode

The correct answer is a Read up on diode applications

2 Differential synchros have

a) a transmitter only

b) a receiver only

c) a transmitter and a receiver

The correct answer is c See Pallett Aircraft Instruments and Integrated Systems pg 135.

3 In an integrated circuit, the components are mounted

a) by means of wires connecting them

b) by metal oxide film

c) by metal screws

The correct answer is b A metal oxide film is etched onto the surface of the IC to make the conductors.

4 This symbol is

a) a diode

b) a triac

c) a transistor

The correct answer is a Learn the electronic component symbols. Aircraft Electricity and Electronics 5th Edition Eismin Page 384

5 One characteristic of the emitter follower is

a) low resistance output

b) low current amplification

c) high voltage amplification

The correct answer is a The emitter follower (common collector) has the lowest output resistance of all three configurations.

6 A reduction from the optimum setting of the velocity feedback in a servo loop could cause

a) low servo gain

b) instability

c) slow response

The correct answer is b See Pallett Automatic Flight Control pg 88.

7 In a torque synchro system, the power supply is connected to

a) the rotor windings of the transmitter only

b) the rotor windings of both the transmitter and receiver

c) the stator windings of the transmitter

The correct answer is b See Pallett Aircraft Instruments and Integrated Systems pg 135. Aircraft Electricity and Electronics 5th Edition Eismin Page 185/6

8 The phase difference between the supplies of a two phase induction motor is

a) 180o

b) 90o

c) 0o

The correct answer is b The phase difference of the two phases applied to an induction motor is 90 degrees.

9 To reduce overshoot errors in a synchro

a) the system will have position feedback

b) the system will have velocity feedback

c) the gain of the amplifier is increased

The correct answer is b Velocity feedback is used to reduce overshoot and oscillations.

10 A synchro transformer is used to

a) derive an error voltage from a synchro transmitter signal and a shaft position

b) obtain a 26 volt AC reference

c) add the output of two synchro transmitters

The correct answer is a See Pallett Automatic Flight Control pg 135.


1 This is a diagram of a

a) differentiator

b) integrator

c) adder

The correct answer is a A differentiator uses a resistor in the feedback loop across the op amp.

2 Reversal of the complete power to a torque synchro system will

a) have no effect

b) cause reverse rotation of the receiver rotor

c) displace the receiver rotor by 180o

The correct answer is a Since both rotors are supplied with the same AC, reversing the connections to both will have no effect.

3 The power supply to a torque synchro system is

a) AC

b) DC

c) AC or DC

The correct answer is a See PAllett Aircraft Instruments and Integrated Systems pg 135.

4 This symbol is

a) an LED

b) a laser diode

c) a photodiode

The correct answer is c The photodiode is used in reverse bias. The minority current increases when light shines on it.

5 When a positive voltage is applied to the base of a normally biased n-p-n common emitter amplifier

a) the emitter current decreases

b) the collector voltage goes less positive

c) the base current decreases

The correct answer is b Sketch the circuit and work it out.

6 An amplifier current gain will be slightly less than 1, but its voltage gain will be high, if it is connected in the

a) common base configuration

b) common emitter configuration

c) common collector configuration

The correct answer is a Only the common base configuration provides a current gain of less than 1.

7 An open loop system is one which has

a) no direct feedback loop

b) rate feedback loop

c) position feedback only

The correct answer is a Open loop has no feedback.

8 Mechanical friction in a servo results in

a) reduced gain

b) increased damping

c) increased inertia

The correct answer is b Friction devices are sometimes used to increase damping and thus decrease oscillations.

9 The position feedback signal is

a) in phase with the input demand signal

b) in anti-phase with the demand signal

c) phase advanced by 90o with respect to the input signal

The correct answer is b The positive feedback must be in anti-phase if it is to oppose the demand input.

10 A servo system that overshoots and oscillates is

a) under damped

b) over damped

c) critically damped

The correct answer is a Oscillations are caused by an underdamped system.


1 The power supply to a torque synchro system is connected to

a) the transmitter stator

b) the transmitter rotor only

c) the transmitter and receiver rotors

The correct answer is c See Pallett Aircraft |Instruments and Integrated Systems pg 135.

2 If the rotor of the receiver in a torque synchro system was prevented from aligning with the transmitter rotor, then

a) the transmitter rotor will turn to align with the receiver rotor

b) the receiver will overheat

c) a high current will flow in the stator windings

The correct answer is c Current flows in the stator whenever the rotor are not in correspondence.

3 This is a diagram of a

a) differentiator

b) integrator

c) adder

The correct answer is b An integrator has the capacitor in the feedback loop across the op amp.

4 A zener diode

a) stabilizes voltage at a predetermined level

b) allows current to flow in one direction

c) acts like a switch

The correct answer is a Zener diodes are usually used in voltage regulator circuits. Aircraft Electricity and Electronics 5th Edition Eismin Page 385

5 The common collector amplifier is sometimes called the emitter follower circuit because

a) the emitter current follows the collector current

b) the emitter voltage follows the base voltage

c) the emitter voltage follows the collector voltage

The correct answer is b Read up on transistor configurations and their respective outputs/inputs.

6 In a toroidal resistance transmitter indicator system, the power supply is connected to

a) the brushes

b) the resistor slab

c) the rotor

The correct answer is a A toroidal resistance indicator is better known as a Desynn indicator.

7 When a servo has reached its null and stopped, the velocity feedback is

a) zero

b) maximum and anti-phase

c) maximum and in phase

The correct answer is a Velocity feedback will stop when the load is at rest.

8 The primary purpose of rate feedback in a positional servo system is to

a) ensure minimum response time

b) prevent excessive overshoot

c) ensure system linearity

The correct answer is b Rate feedback is to prevent excesive overshoot and oscillation.

9 In an AC rate servo, a steady input will result in the servomotor

a) oscillating about a new datum

b) rotating at a constant speed

c) rotating to a new datum position

The correct answer is b An AC rate servo is designed to rotate a load (such as a radar dish) at a constant speed continually.

10 An E&I bar output at datum has

a) no induced voltage in the secondary windings

b) an imbalance of voltages in the secondary windings

c) equal and opposite voltages induced in the secondary

The correct answer is c See Pallett Automatic Flight Control pg 130.


1 A non-inverting op-amp

a) has a non-inverting input and an inverting output

b) has an inverting input and a non-inverting output

c) a non-inverting input connection only

The correct answer is c Read up on op amps.

2 Amplifiers may be classified as

a) common emitter or common collector amplifiers

b) voltage amplifiers or impedance amplifiers

c) voltage amplifiers or power amplifiers

The correct answer is c Amplifiers are classified as either voltage or power amplifiers.

3 What is a shottky diode used for?

a) Very high frequency applications

b) Stabilsation

c) Rectification

The correct answer is a A shottky diode has very little junction capacitance and can be used for very high frequency swiching applications.

4 The result of cross connecting two of the transmission leads in a torque synchro system and then turning the rotor of the transmitter 60o clockwise would be

a) the receiver would move 60o clockwise

b) the receiver would move 120o anticlockwise

c) the receiver would move 60o anticlockwise

The correct answer is c Read up on synchro faults.

5 The control windings of a two phase servomotor is supplied with AC voltage of

a) constant amplitude

b) variable phase

c) variable amplitude, variable phase

The correct answer is c The control windings are fed with variable amplitude AC but the amplitude can be positive (in phase) or negative (anti-phase).

6 In a torque synchro that includes a differential synchro the power supply is connected to

a) the transmitter rotor only

b) the transmitter and receiver rotors only

c) all three rotors

The correct answer is b See Pallett Aircraft Instruments and Integrated Systems pg 135.

7 A differential synchro rotor has

a) three windings

b) two windings

c) one winding

The correct answer is a See Pallett Aircraft Instruments and Integrated Systems pg 135.

8 If the rotor of a control synchro sticks

a) the system hunts

b) high current will flow

c) the position feedback will oscillate

The correct answer is b High current flows in the stators whenever the rotors are not in correspondence.

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

a) unchanged

b) changed by 120o

c) changed by 180o

The correct answer is c Read up on synchro faults

10 The application of a 'stick-off' voltage to a control synchro servo system is

a) to overcome the effect of static friction

b) to overcome the effect of viscous friction

c) to prevent alignment to a false null

The correct answer is c Stick-off voltage is to prevent alignment to a false null (i.e. 180 degrees out) when system is switched off.


1 When removing a microprocessor

a) no damage is done by static discharge

b) considerable damage can be done by static discharge

c) ensure the power is OFF to avoid static discharge

The correct answer is b Read up on microprocessors.

2 An amplifier can provide both voltage gain and current gain when it is connected in the

a) common base configuration

b) common emitter configuration

c) common collector configuration

The correct answer is b Only the common emitter configuration provides both current and voltage gain greater than 1.

3 How do you increase voltage gain of an amplifier?

a) decrease base circuit bias

b) decrease input resistance

c) increase input resistance

The correct answer is b Amplifier gain = feedback resistance / input resistance.

4 In a resolver synchro the stator windings are electrically displaced by

a) 90o

b) 120o

c) 180o

The correct answer is a See Pallett Aircraft Instruments and Integrated Systems pg 135.

5 A servo system may include a brake, an automatic trim system is one example where a brake is used. The brake is

a) applied during trimming to prevent oscillations about the demand position

b) applied when trimming is complete to prevent stabilizer creep

c) applied during trimming to prevent servo runaway

The correct answer is b The trim switch often consists of 2 separate switches. One is to release the brake, the other is to switch on the motor.

6 A resolver synchro output is obtained from a rotor with

a) one single coil

b) three coils at 120o

c) two coils at 90o


7 In a control synchro the stator current ceases to flow when

a) the CT rotor is at null

b) when the two rotors are aligned

c) when power is removed

The correct answer is c In a control synchro, the stator is supplied with current at all times, whatever the transformer rotor position.

8 In a speed control servo system (rate control), the purpose of the tachogenerator is

a) to make the velocity proportional to servo demand

b) to make the deflection proportional to servo demand

c) to make it run at constant speed

The correct answer is c The tachogenerator is to make the load rus at a constant speed.

9 The result of reversing the rotor connections to the receiver of a torque synchro system is that the rotor position

a) is unchanged

b) is changed by 120o

c) is changed by 180o


10 The rotor of a torque synchro indicator is

a) supplied with an excitation voltage

b) short circuited

c) connected in series with the transmitter stator coil

The correct answer is a The excitation voltage is that necessary to magnetise the rotor.


1 When a hole diffuses from a p-region to the n-region it

a) becomes a minority carrier in the n-region

b) lowers the potential barrier

c) raises the potential barrier

The correct answer is c This is decriptive of holes crossing the PN junction to form the depletion layer. Aircraft Electricity and Electronics 5th Edition Eismin Page 111

2 How are the pins numbered on an op-amp IC?

a) counter clockwise from the dot

b) clockwise from the dot

c) from left to right from the dot

The correct answer is a Pins on an IC are always numbered counter-clockwise from the dot. Aircraft Electricity and Electronics 5th Edition Eismin Page 140

3 To increase the output of a servo amplifier, it is necessary to

a) reduce the tacho feedback

b) increase the tacho feedback

c) increase the position feedback

The correct answer is a Tachogenerator feedback opposes the error signal and thus reduces amplifier output.

4 Angular displacement of the control coils with respect to the reference coils in a two phase induction motor are

a) 0o, 180o

b) 90o, 270o

c) 90o, 120o

The correct answer is b Read up on induction motors.

5 a two phase induction motor used in a servomechanism

a) will always require a starter

b) is self starting under light loads

c) runs with no slip

The correct answer is b Read up on induction motors.

6 A servomotor having only a tachogenerator as a feedback device will

a) vary its speed with input error voltage

b) have a constant speed for any given input voltage

c) null out at a position dependant upon input error voltage

The correct answer is b With only a tacho feedback it is a rate servo.

7 A hysteresis servo motor is used in a servomechanism because

a) it has good starting characteristics

b) good speed/voltage relationship

c) low inertia

The correct answer is a Read up on the hysteresis motor.

8 The null position of a torque synchro system is when

a) the TX and TR rotors are parallel to each other

b) the TX and TR rotors are 90o to each other

c) the TX and TR rotors are 120o to each other

The correct answer is a TX and TR rotors must be parallel to be at the null position.

9 Reversal of two of the stator connections on a torque synchro receiver would cause

a) the transmitter to become the receiver

b) the output to move the same direction as the input

c) the output to move the reverse direction to the input


10 An AC tachogenerator stator has

a) two windings 180o apart

b) three windings 120o apart

c) two windings 90o apart

The correct answer is c Read up on the tachogenerator.


1 A junction diode

a) has one p-n junction

b) is similar to a vacuum diode but cannot rectify

c) can handle only very small currents

The correct answer is a Read up on the diode definitions. Aircraft Electricity and Electronics 5th Edition Eismin Page 111

2 When the rotor of an AC tachogenerator is stationary, the rotor has

a) no circulating currents

b) low circulating currents

c) no magnetic fields

The correct answer is b A small amount of residual voltage exists on the output winding of an AC tachogenerator when it is stationary.

3 The output of a tachogenerator should be

a) sinusoidal

b) exponential

c) linear

The correct answer is a The output should be the same waveform as the input, i.e. sinusoidal.

4 With a constant input to a speed control servo, the servo motor

a) moves to a certain position

b) moves at a constant speed

c) oscillates, but otherwise does not move

The correct answer is b A speed control servo moves the load (e.g. a radar dish) at constant speed.

5 A closed loop servomechanism

a) must only have position feedback

b) must have both position and velocity feedback

c) can have either position or velocity feedback

The correct answer is c A closed loop servomechanism can have either position feedback or velocity feedback or both.

6 Critical damping in a servomechanism is

a) the point which allows just one overshoot before the load comes to rest

b) the amount of damping that results in the load just not oscillating

c) the critical damping required for the optimum damping of the servomechanism

The correct answer is b Critical damping results in the fastest time to demand position without any overshoot.

7 In a control synchro system the power supply is connected to the

a) transmitter rotor and amplifier

b) receiver rotor and amplifier

c) transmitter and receiver rotors

The correct answer is a See Pallett Aircraft Instrumants and Integrated Systems pg 141.

8 Reverse rotation of a control transformer rotor can be caused by

a) connections between the transformer rotor and the amplifier reversed

b) connections to the transmitter rotor reversed

c) short circuit between two transmission lines

The correct answer is a Reversing the connections to the amplifier will make the motor run backwards. Then the feedback will drive the transformer rotor in the wrong direction.

9 Velocity feedback

a) opposes the demand input

b) assists the demand input

c) prevents dead space errors

The correct answer is a Velocity feedback is anti-phase to the demand input and opposes it.

10 Velocity lag can be decreased by

a) introduction of an integrator

b) keeping the error detector (summing point) output as low as possible

c) decreasing the coulomb friction in the system

The correct answer is c Coulomb friction is one of the things which causes velocity lag.


1 The junction barrier offers opposition to only

a) holes in the p-region

b) free electrons in the n-region

c) majority carriers in both regions

The correct answer is c Read up on semiconductor theory.

2 An increase in velocity feedback will

a) decrease the speed the load moves

b) increase the speed the load moves

c) have no effect on speed

The correct answer is a Velocity feedback opposes demand input therefore it reduces thew speed the load moves.

3 A two phase motor will stop when

a) the reference phase is reversed

b) the control phase is reversed

c) the control phase is zero

The correct answer is c A two phase motor will stop when the control phase is zero (i.e. no output).

4 A tachogenerator output is

a) variable frequency, constant voltage

b) variable voltage, constant frequency

c) variable frequency, variable voltage

The correct answer is b A tachogenerator output is the same frequency as the input (i.e. constant) but the voltage varies.

5 Rate feedback can be obtained from a

a) synchro

b) tachogenerator

c) potentiometer

The correct answer is b A tachogenerator produces rate feedback.

6 Positional feedback can be obtained from a

a) synchro

b) tachogenerator

c) potentiometer

The correct answer is c A potentiomenter produces positional feedback

7 The frictional force in a servomechanism that is proportional to speed is called

a) stiction

b) coulomb friction

c) viscous friction

The correct answer is c Viscous friction is proportional to speed.

8 The 'null' point in a control synchro is when the two rotors are

a) at 90o to each other

b) parallel to each other

c) wired in series

The correct answer is a 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).

9 If two of the stator leads are cross connected in a control synchro system, a 25o clockwise rotation of the input rotor would result in the output rotor

a) moving 25o clockwise

b) moving 25o anticlockwise

c) moving 180o to rectify the defect

The correct answer is b 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.

10 Damping in a servomechanism is easier to apply if

a) the mechanism is light and has low inertia

b) the mechanism is heavy and has high inertia

c) the mechanism is light and has high inertia

The correct answer is a Overshoot and oscillation is greatest when the mechanism is heavy and has a high inertia.


1 Reverse bias

a) lowers the potential barrier

b) raises the potential barrier

c) greatly increases the majority carrier current

The correct answer is b Read up on semiconductor theory.

2 If the electrical connections to the feedback generator in a control synchro system were disconnected, the

a) motor would run in the wrong direction

b) input signal to the amplifier would reduce

c) system would tend to oscillate

The correct answer is c Feedback from the tachogenerator prevents overspeed and overshoot, so disconnecting the feedback will cause the load to overshoot and oscillate.

3 An increase in servo amplifier gain

a) reduces the speed of the system

b) increases system response

c) reduces tendency to hunt

The correct answer is b Increasing servo-amplifier gain will make the system respond faster but will also cause it to overshoot and oscillate (hunt).

4 In a control synchro the stator current ceases to flow when the

a) CT rotor is at null

b) two rotors are aligned

c) power is removed

The correct answer is c In a control synchro current flows in the stator lines at all times, regardless of the position of the tarnsformer rotor.

5 The term 'velocity lag' refers to a

a) speed error

b) position error

c) acceleration error

The correct answer is b Velocity lag is the difference between the demand input and the load position. It is therefore a position error.

6 The rotor of an AC tachogenerator

a) has skewed slots

b) has a copper, brass or aluminium cylinder

c) rotates at constant speed

The correct answer is b An AC generator rotor is made from a diamagnetic material such as copper, brass or aluminium.

7 A servo system with transient negative velocity feedback

a) is damped with little velocity lag

b) is damped with high velocity lag

c) is underdamped with high velocity lag

The correct answer is a 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.

8 To reverse the direction of rotation of a two phase induction motor

a) reverse the polarity of the control phase

b) reverse the polarity of both the control phase and reference phase

c) shift the reference by 90o

The correct answer is a To reverse the direction of a two phase induction motor the control phase must be out of phase with the reference phase.

9 In a rate servo (speed control) the signal into the servo amplifier is

a) input voltage plus tachogenerator output

b) input voltage minus tachogenerator output

c) input voltage plus position feedback voltage

The correct answer is b In a rtate servo the input voltage makes the load rotate and the tachogenerator output (which is negative feedback) prevents it rotating too fast.

10 Loss of DC to a servo amplifier causes the motor to

a) run continuously

b) stop

c) reverse

The correct answer is b Loss of DC to the servo-amplifier will cause the amplifier to stop working and the motor will therefore stop running.


1 Avalanche breakdown occurs when

a) forward current becomes excessive

b) forward bias exceeds a certain value

c) reverse bias exceeds a certain value

The correct answer is c Reverse biasing a diode will cause avalanche breakdown at a certain value. Aircraft Electricity and Electronics 5th Edition Eismin Page 120

2 An AC servo demand can be converted to drive a DC motor by the introduction of a

a) rectifier

b) modulator

c) demodulator

The correct answer is c 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.

3 Synchro indicator systems are used when the indication is required to move

a) a fraction of the input distance

b) slower than the input rate

c) at the same rate as the input

The correct answer is c A synchro indicator moves at the same speed as the input.

4 A linear variable differential transformer is used to measure position feedback where

a) 360o of rotation and high angular accuracy is required

b) accuracy is of limited importance but robust construction and reliability is important

c) an output whose phase is related to direction of movement and amplitude linear over a wide range

The correct answer is c An LVDT measures position and provides a different phase according to the direction of movement.

5 A low frequency sinusoidal input will cause a closed loop servomechanism load to

a) move to a demand position with no overshoot

b) move backwards and forwards at the input frequency

c) move to the demand position and then return to the datum position without any overshoot

The correct answer is a A closed loop servo mechanism (whatever frequency) will move to the demand position with no or minimal overshoot.

6 To reduce oscillations about a demand position

a) the amount of velocity feedback would be decreased

b) the amount of velocity feedback would be increased

c) the amount of position feedback would be increased

The correct answer is b If velocity feedback is increased, there is more opposition to the demand signal and the load will move slower and oscillations will be reduced.

7 If a servo amplifier is suffering from drift

a) the load would move to a new position, proportional to the drift and stay there

b) the load would move to a new position, proportional to the drift and then return back to the datum position

c) the load would oscillate about the datum position

The correct answer is a 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.

8 In a transient velocity feedback circuit, the tachogenerator output is summated with the demand voltage

a) only when the load is slowing down

b) at all times when the load is moving

c) only when the load is speeding up or slowing down

The correct answer is c Automatic Flight Control EHJ Pallett Page 91.

9 Positive feedback applied to a servomechanism

a) decreases the response of the system

b) opposes the demand signal

c) increases the response of the system

The correct answer is c Positive feedback will add to the input of the amplifier and increase the response of the system.

10 A differential synchro rotor consists of

a) one winding parallel to the transmitter rotor

b) two windings at 90o apart

c) three windings at 120o apart



1 A differential synchro transmitter used for addition has

a) the TDX S1 and S3 connections cross connected to the TX

b) the TDX S1 and S3 connections cross connected to the TR

c) the TDX R1, R3 and S1, S3 connections cross connected to the TX

The correct answer is c 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.

2 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

a) only after the forward bias exceeds the potential barrier

b) when the flow of minority carriers is sufficient to cause an avalanche breakdown

c) when the depletion layer becomes larger than the space charge area

The correct answer is a A forward biased PN junction will conduct only when the forward bias voltage exceeds the juction barrier - i.e Si = 0.6V, Ge = 0.2V

3 An LVDT has

a) an output winding which is wound in series opposition

b) an input winding whose voltage will change with load movement

c) an output winding whose voltage and frequency is linear to load angular movement

The correct answer is a An LVDT has an output winding which is wound in series opposition.

4 A diode connected across a relay coil is used to

a) allow the coil to energize with only one polarity

b) cause a delay in switching on

c) dissipate coil spikes on switch off

The correct answer is c A diode connected accross a relay coil is to dissipate the voltage spike when the relay coil de-energises. Aircraft Electricity and Electronics 5th Edition Eismin Page 121

5 Differential transmitters are used to

a) add or subtract two electrical signals

b) add or subtract a mechanical signal to an electrical synchro signal

c) increase the operating speed of the synchro receiver

The correct answer is b A differential synchro is used to add or subtract a mechanical signal from an electrical signal derived from the synchro transmitter.

6 To convert a differential synchro from subtraction to addition you would

a) reverse the reference phase supply

b) change over two rotor and stator connections

c) change over all three stator windings

The correct answer is b To convert a differential synchro from subtraction to addition you must swap two of the rotor leads AND swap two of the rotor leads.

7 What is resistor R used for?

a) Amplification

b) Bias

c) Stabilisation

The correct answer is c The resister R is used to provide thermal stabilisation to the transistor by supplying negative feedback if the quiescent point moves.

8 When resolving a Cartesian input to a Polar output

a) the inputs are a shaft angle and a voltage

b) the outputs are two voltages

c) the inputs are two voltages

The correct answer is c 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.

9 To check the forward resistance of a diode with a multimeter, the lead connected to the positive terminal is put to the

a) anode

b) cathode

c) either anode or cathode

The correct answer is a 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.

10 A resolver synchro output is obtained from a rotor with

a) one single coil

b) two coils at 90o to each other

c) three coils at 120o to each other

The correct answer is b A resolver synchro has two coils at 90 degrees to each other.


1 The input and output signals of a common emitter amplifier are

a) equal

b) out of phase

c) in phase

The correct answer is b The common emitter amplifier is the only configuration which provides an output which is anti-phase with the input.

2 The output of a resolver synchro is

a) dependant upon the position of the rotor only

b) proportional to the speed of input rotation

c) a function of the rotor position and excitation voltage

The correct answer is c The output of a resolver synchro is angular position and a voltage to represent the distance.

3 The rotor of an autosyn position indicating system is

a) a permanent magnet

b) an electromagnet

c) spring controlled

The correct answer is b The rotor of an autosyn position indicating system is an electromagnet.

4 A band pass filter excludes frequencies

a) above the frequency required only

b) below the frequency required only

c) above and below the frequency required

The correct answer is c A band-pass filter excludes frequencies above and below a particular frequency. Aircraft Electricity and Electronics 5th Edition Eismin Page 288

5 The rotor of a magnesyn transmitter is

a) a dc electromagnet

b) a permanent magnet

c) an ac electromagnet

The correct answer is b The rotor of a magnesyn transmitter (and reciever) is a permanent magnet.

6 In general the accuracy of a synchro system increases if the

a) stator current is high

b) stator current is low

c) rotor current is high

The correct answer is b The synchro system is only accurate when the two rotors are in correspondence. At this time the stator current is zero.

7 Torque synchro systems are normally used when the

a) mechanical load is low

b) mechanical load is high

c) system accuracy is of extreme importance

The correct answer is a Torque synchros are used for indication only, i.e. when the load is low.

8 In a resolver synchro the stator windings are electrically disposed by

a) 90o

b) 120o

c) 180o

The correct answer is a A resolver synchro has the windings 90 degrees apart.

9 The induced signal in the output coils of the magnesyn system

a) de-saturates the soft iron core

b) damps the pointer oscillations

c) is of a value of 800 Hz

The correct answer is c 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.

10 The direction of the induced (secondary) magnetic field in a synchro transmitter

a) is 90o to the primary magnetic field

b) in the same direction as the primary field

c) is in the opposite direction to the primary field

The correct answer is c 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).


1 The cogging effect in synchros is rectified by

a) using carbon brushes

b) using an elliptical cog

c) skewing the rotor

The correct answer is c The cogging effect in a synchro is prevented by skewing (or twisting) the rotor.

2 A transistor is said to be in the quiescent state when

a) no signal is applied to the input

b) it is unbiased

c) no currents are flowing

The correct answer is a The quiescent state of a transistor is when DC is supplied to the base to bias the transistor. No signal is applied.

3 In an unbiased p-n junction, current flow is

a) due to the diffusion of minority carriers only

b) zero, because no charges are crossing the junction

c) zero, because equal but opposite currents are crossing the junction

The correct answer is b Read up on semiconductor theory.

4 Reversal of the power supply to either the transmitter or the receiver of a torque synchro system would

a) cause a 180o displacement between the transmitter and the receiver

b) have no effect on the indication, but would cause a heavy current to flow

c) make the receiver rotor rotate in the opposite direction

The correct answer is a Reversal of the power supply to either the transmitter or the receiver will cause a 180 degree displacement of the receiver rotor.

5 Torque synchro systems are normally used when the

a) mechanical load is low

b) mechanical load is high

c) system accuracy is of extreme importance

The correct answer is a A torque synchro is only used for indication - i.e. the load is low.

6 A common base transistor circuit is so called because

a) the base region is located between the emitter and collector region

b) the base is n-type material

c) the base is common to the emitter and collector circuits

The correct answer is c Read up on the three transistor amplifier configurations.

7 What device transfers one energy type to another?

a) Transmitter

b) Transducer

c) Transponder

The correct answer is b The device that transfers one energy type to another is called a transducer. Aircraft Electricity and Electronics 5th Edition Eismin Page 171

8 Which way does conventional current flow in a PNP junction?

a) Collector to emitter

b) Emitter to base

c) Collector to base

The correct answer is b Conventional current in a PNP transistor flows from EMITTER to BASE. Note: In an NPN transistor it would be collector to emitter.

9 Electrical power is supplied to a synchro rotor

a) directly

b) through slip rings

c) through a commutator

The correct answer is b Electrical power is connected to a synchro rotor through slip rings.

10 The purpose of a flywheel incorporated in a synchro is to

a) increase the driving force

b) prevent oscillations

c) prevent insect ingress

The correct answer is b The purpose of a flywheel on a synchro is as part of a eddy current (coulomb friction) damping mechanism.


1 In an operational amplifier, the two input waves are the same amplitude, same frequency, but exactly anti-phase. What would the output be?

a) Double

b) Zero

c) Half

The correct answer is a Although the input waves are anti-phase, the inerter input of the op amp inverts one of the inputs, so the two waves actually add to each other.

2 A thyristor has which of the following?

a) High resistance when switched on

b) High resistance when switched off

c) A positive temperature coefficient

The correct answer is b The thyrister (such as an SCR or TRIAC) is basically a switch which provides a high resistance when switched off.

3 On an integrated circuit the hole in the top left corner is pin 1. The pins are counted

a) clockwise

b) anticlockwise

c) from left to right

The correct answer is b On an IC the pins are counted anti-clockwise. Aircraft Electricity and Electronics 5th Edition Eismin Page 140

4 With reference to the circuit shown below, how is the transistor configured?

a) Common emitter

b) Common collector

c) Common base

The correct answer is a The diagram shows a common emitter circuit.

5 In the circuit diagram above, R1 and R2 are used to

a) set the transistor gain

b) set the DC bias level

c) increase the base voltage

The correct answer is b The resistors R1 and R2 are to set the bias level of the transistor, i.e. to put the transistor into quiescence.

6 In a synchro system, if two stator lines are crossed the receiver will

a) not be affected

b) be 180o out

c) reverse direction

The correct answer is c If two stator lines are crossed the receiver will reverse in direction.

7 In the following Boolean algebra statement, which gate is described?

F = A + B + C

a) Or

b) Not

c) And

The correct answer is a A+B+C represents an OR gate.

8 In an E and I signal generator at datum, the voltage on the secondary windings

a) are equal and opposite

b) is maximum

c) is zero

The correct answer is a 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.

9 In a synchro resolver, the stator coils are at what angle in relation to one another?

a) 45 degrees

b) 80 degrees

c) 90 degrees

The correct answer is c in a synchro resolver the stator coils are 90 degrees to each other.

10 In a synchrotel, the

a) rotor coil is fixed and the stator coil moves

b) rotor coil and stator coil is fixed

c) stator coil is fixed and the rotor coil moves

The correct answer is b Aircarft Instruments and Integrated Systems Pallett Page 149/150


1 On a PCB, a decoupling capacitor is used to get rid of transient currents between which points?

a) The electronic circuit and the aircraft ground

b) Interspaced along the circuit

c) The negative rail and the rest of the circuit

The correct answer is b The decoupling capacitor decouples the AC signal from the DC quiescent current.

2 What does the circuit shown below do?

a) Full wave rectifier

b) Voltage doubler

c) Half wave rectifier

The correct answer is c The diagram shows a half wave rectifier. The capacitor is for smoothing the output. A full wave rectifer requires 4 diodes and a voltage doubler requires two capacitors.

3 In an LED, what is used to make the colour?

a) The doping material

b) The electrons

c) The plastic lens cover

The correct answer is a The dopant is what gives the LED its colour.

4 An atom with 5 electrons in its outer shell is part of

a) an N type material

b) a P type material

c) a C type material

The correct answer is a 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

5 In a FET, the junction connections are called

a) drain, source and gate

b) base, collector and emitter

c) drain, collector and junctions

The correct answer is a The leads of a FET are called drain, source and gate. Aircraft Electricity and Electronics 5th Edition Eismin Page 120

6 In the Boolean algebra statement below, the gate described is

F = A.B.C

a) Nand

b) Nor

c) And

The correct answer is c A.B.C represents an AND gate.

7 With a small amplitude voltage, what type of diode would you use to produce the output waveform?

a) Shottky

b) Gunn

c) Zener

The correct answer is a 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.

8 An increase in negative feedback to the servo amplifier

a) increases amplifier stability

b) decreases amplifier stability

c) has no effect

The correct answer is a Negative feedback helps to increase the stability of an amplifier with changes in temperature and the effects of age.

9 How is a push-pull transistor arrangement connected?

a) emitter to emitter

b) collector to collector

c) base to base

The correct answer is a A push pull amplifier is wired emitter to emitter.

10 Thermal runaway in a transistor is caused by

a) excessive heat causing maximum current flow

b) excessive heat causing minimum current flow

c) low heat causing minimum current flow

The correct answer is a Thermal runaway is caused by excessive temperature creating an increase in current flow and hence an increase in temperture etc. etc..


1 A single integrated circuit Op Amp has how many pins?

a) 4

b) 7

c) 8

The correct answer is c 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

2 What is the output of the amplifier shown below?

a) 0V

b) 3V

c) 5V

The correct answer is c A basic adding op-amp. 4 + 0 + 1 = 5

3 A thyristor is commonly used for

a) voltage regulation

b) overvolts regulation

c) rectification

The correct answer is c A thyrister (especially an SCR) is often used for rectification.

4 A diode which emits photons when conducting is a

a) zener

b) varactor

c) light emitting

The correct answer is c Photons = light, so a diode which emits light is a Light Emitting Diode.

5 Avalanche breakdown occurs when

a) forward bias becomes excessive

b) forward bias exceeds a certain value

c) reverse bias exceeds a certain value

The correct answer is c Avalanche breakdown occurs when reverse bias exceeds a certain value.

6 The electrodes of an SCR are

a) anode, cathode, source

b) source, drain, gate

c) gate, cathode, anode

The correct answer is c The electrodes of an SCR are the anode, cathode and the gate. Aircraft Electricity and Electronics 5th Edition Eismin Page 120

7 What gives an LED its colour?

a) A gas

b) The cover

c) Composition and impurity of the compound

The correct answer is c It is the doping element which gives an LED its colour.

8 For conduction of a transistor the emitter junction is

a) fwd biased

b) reverse biased

c) fwd or reverse as appropriate to the input signal

The correct answer is a 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

9 In a PNP transistor which way does conventional current flow

a) base to emitter

b) collector to emitter

c) emitter to collector

The correct answer is c In a PNP transistor, the main current flow is Emitter to Collector (reverse of what it is with an NPN transistor).

10 Infinite gain, infinite input impedance & zero output impedance is characteristic of a

a) Class A amp

b) Class B amp

c) Op amp

The correct answer is c Infinite gain, infinite input impedance and zero output impedance are characteristics of the ideal op amp.


1 Forward voltage of a silicon diode is

a) 0.6V

b) 0.2V

c) 1.6V

The correct answer is a Si = 0.6V, Ge = 0.2V Aircraft Electricity and Electronics 5th Edition Eismin Page 111 or 113

2 An advantage of a common emitter is

a) it is a voltage follower

b) it has high power gain

c) it has high voltage gain

The correct answer is b Common emmitter configuration has a high power gain.

3 What amplifier is biased at cut off

a) A

b) B

c) C

The correct answer is b Read up on amplifier types. Aircraft Electricity and Electronics 5th Edition Eismin Page 281

4 When testing a transistor with an ohmmeter, what is the resistance of the emitter/collector?

a) High resistance one way

b) High resistance both ways

c) Low resistance both ways

The correct answer is b 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

5 What is the typical volts drop across an LED

a) 1.6V

b) 0.2V

c) 0.4V

The correct answer is a An LED volts drop is typically 1.6 - 2.4V. Aircraft Electricity and Electronics 5th Edition Eismin Page 121

6 What diode gives off light photons when forward biased

a) LED

b) Shottky diode

c) Gunn diode

The correct answer is a LEDs give off light (photons) when forward biased.

7 A logic circuit with more than one gate will have

a) one of 2 states of logic output

b) 2 or more outputs

c) an analogue output

The correct answer is a Logic circuit outputs are either 0 or 1, regardless of the number of gates in the circuit.

8

This is a diagram of

a) an SCR

b) a transistor

c) a photo diode

The correct answer is c Learn the electronic component symbols. Aircraft Electricity and Electronics 5th Edition Eismin Page 385

9 In a synchro, what is used to convert signals from one form to another?

a) Transmitter

b) Transducer

c) Transformer

The correct answer is b A 'transducer' converts one signal type to another. Aircraft Electricity and Electronics 5th Edition Eismin Page 171

10 Components on an integrated circuit are

a) in the solid

b) don't need them

c) on the surface

The correct answer is c Components on an integrated circuit are on the surface of the substrate.


1 What diode is used to stop power spikes in a coil?

a) Two directional zener diode

b) Shottky diode

c) Gunn diode

The correct answer is a A two directional zener diode (actually 2 zener diodes back-to-back) is used to stop power spikes.

2 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

a) forward biased not conducting

b) reverse biased not conducting

c) forward biased conducting

The correct answer is c Forward bias is anode to cathode. 4V fwd bias and 2V reverse bias, the diode is 2V fwd bias in total.

3 Using electron flow in a diode the current flows from

a) Anode to Cathode

b) Cathode to Anode

c) Cathode to Base

The correct answer is b ELECTRON FLOW (i.e. American notation) is cathode to anode (against the arrow direction). Aircraft Electricity and Electronics 5th Edition Eismin Page 111

4 A control surface position feedback signal is

a) proportional to surface position

b) inversely proportional to surface position

c) non-linear

The correct answer is a Position feedback is proportional to surface position. Meaning, as control surface deflection increases, so does the feedback.

5 In a PNP transistor, conventional current will flow when

a) the emitter is more positive than the base

b) the base is more positive than the emitter

c) the collector is more positive than the emitter

The correct answer is a To switch a PNP on, the emitter must be positive compared to the base (opposite to an NPN).

6 An E&I transformer out of datum has

a) equal and opposite voltages in each windings

b) unequal and opposite voltages in both windings

c) no voltage in either winding

The correct answer is b Off datum, the E&I transformer has unequal and oppsite voltages in the windings (and hence an output).

7 A gyro will provide

a) rate feedback

b) velocity feedback

c) positional feedback

The correct answer is c Presumably they are referring to a 'position gyro' (as in artificial horison and directional gyro) and not a 'rate gyro' (as in the slip indicator). The latter would make a) nad b) correct anyway since rate and velocity are the same thing. Worth a comment on the exam paper if you get this.

8 In a common collector circuit the output and input are

a) out of phase by 90o

b) in phase

c) out of phase by 60o

The correct answer is b Common collector - output is in-phase with the input.

9 In velocity feedback the signal is

a) in phase

b) out of phase

c) equal to the error signal

The correct answer is b The velocity feedback must be anti-phase with the error signal in order to oppose it (and thus be negative feedback).

10 When a hole diffuses from the p region to the n region

a) it becomes a minority carrier in the n region

b) lowers the potential barrier

c) raises the potential barrier

The correct answer is c 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).


1 A junction diode

a) has one p-n junction

b) is similar to a vacuum diode but cannot rectify

c) can handle only small currents

The correct answer is a A junction diode is so named for its one junction. Aircraft Electricity and Electronics 5th Edition Eismin Page 111

2 A germanium diode is used for

a) voltage stabilisation

b) rectification

c) signal detection

The correct answer is b A germanium diode is used for rectification. Aircraft Electricity and Electronics 5th Edition Eismin Page 110

3 A germanium diode

a) has a lower forward bias voltage than a silicon diode

b) has a higher forward bias voltage than a silicon diode

c) has the same forward bias voltage as a silicon diode

The correct answer is a Forward bias voltage of germanium diode = 0.2 V. Silicon diode = 0.6 V. Aircraft Electricity and Electronics 5th Edition Eismin Page 111

4 a VLSIC has

a) less than 1000 gates

b) more than 1000 gates

c) more than 10,000 gates

The correct answer is b VLSIC = Very Large Scale Integrated Circuit (> 1,000 gates). Aircraft Electricity and Electronics 5th Edition Eismin Page 138

5 A momentary input at the reset input of a flip flop will

a) reset the true output to 0

b) reset the true output to 1

c) clock in new data from the data inputs

The correct answer is a When the value on reset (R) is 1, the value of Q is set to 0 and vice versa.

6 Which type of flip flop has only 1 data input

a) RS

b) JK

c) D

The correct answer is c The D type Flip Flop has only 1 input (besides the clock input).

7 A low pass filter has

a) a capacitor in series and an inductor in parallel

b) a capacitor in parallel and an inductor in series

c) both capacitor and inductor in parallel

The correct answer is b Read up on low pass, high pass, band stop and band pass filters. Aircraft Electricity and Electronics 5th Edition Eismin Page 143

8 When you use an op amp as a buffer it has

a) high input impedance and low output impedance

b) low input impedance and high output impedance

c) the same input an output impedance

The correct answer is a An op amp is characterised by its high input impedance and low output impedance. Aircraft Electricity and Electronics 5th Edition Eismin Page 288

9 What switches off a thyristor?

a) Remove the gate voltage

b) Remove supply voltage

c) Reverse bias gate

The correct answer is b To switch off a thyristor (such as an SCR) you must disconnect the supply voltage. Aircraft Electricity and Electronics 5th Edition Eismin Page 120

10 When an SCR is switched on it has

a) high resistance

b) low resistance

c) no change in resistance

The correct answer is b An SCR is basically a switch, which, when switched on has a low resistance. Aircraft Electricity and Electronics 5th Edition Eismin Page 120


1 What is required for the switching of a monostable multivibrator

a) one trigger pulse to switch on and another to switch off

b) one trigger pulse to both switch on and off

c) one trigger pulse to switch on and two trigger pulses to switch off

The correct answer is b Monostable multivibrators can remain only in one state permanently. When an external trigger pulse is applied, the circuit moves from its permamnent stable state then drops back after a short while.

2 A transistor at saturation has

a) high resistance

b) low resistance

c) zero resistance

The correct answer is b A transistor at saturation is switched on - therefore has low resistance.

3 A capacitor resistor coupled multistage amp lets

a) AC and DC pass to the next stage

b) AC pass only

c) DC pass only

The correct answer is b A capacitor lets AC pass only.

4 An oscillator operating at its natural frequency has feedback which is

a) inphase

b) 90 degrees out of phase


The correct answer is a An oscillator provides positive inphase feedback to switch itself over.

5 What type of diode when forward biased holes and electrons recombine producing photons?

a) gunn

b) LED

c) photodiode

The correct answer is b The word 'photons' imples light emission - i.e. a light emitting diode (LED).

6 What type of pulse is required to switch on a SCR

a) positive

b) negative

c) positive and negative

The correct answer is a A positive pulse is required to switch an SCR on.

7 Which mathematical operation is performed by a modulator amplifier?

a) Addition

b) Subtraction

c) Multiplication

The correct answer is c A modulator amplfier is a basic input/output amplifier used for amplifying a signal. It 'multiplies' the input signal by the value of the gain.

8 What is meant by a bistable circuit?

a) The circuit has 2 stable states and will stay in which one it is put

b) The circuit has 2 stable states and will stay in both at the same time

c) The circuit has 1 stable state and it can be negative or positive

The correct answer is a A bistable circuit has 2 stable states and it will be in only one at a time.

9 A zener diode is designed to operate

a) above its breakdown voltage

b) below its breakdown voltage

c) either above or below its breakdown voltage

The correct answer is a A zener diode is designed to operate above its breakdown voltage continuously. Aircraft Electricity and Electronics 5th Edition Eismin Page 120

10 A JFET is

a) voltage sensitive

b) current sensitive

c) either of the above depending on resistance in the circuit

The correct answer is a A JFET is voltage sensitive, whereas a normal transistor is current sensitive. Aircraft Electricity and Electronics 5th Edition Eismin Page 119


1 A triac is a type of

a) thyristor

b) thermistor

c) transistor

The correct answer is a Thyristors include, SCRs, Triacs and diacs. Aircraft Electricity and Electronics 5th Edition Eismin Page 120

2 A piece of pure Germanium

a) has a deficit of electrons

b) is electrically stable

c) has an excess of electrons

The correct answer is b 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

3 If a junction diode is reverse biased too far, the output current would

a) cease to flow

b) increase

c) reverse direction

The correct answer is b If a junction diode is reverse biased too far, it will 'breakdown' and a high current will flow.

4 An RC connected amp has

a) no AC across

b) no DC across

c) even amounts of d.c and a.c across

The correct answer is b The purpose of the capacitor between amplifier circuits is to block the DC. Hence only AC is fed across the amplifier

5 When a PN junction is forward biased, it conducts via

a) majority carrier

b) minority carrier

c) intrinsic carrier

The correct answer is a Forward biased - majority carriers

6 Thermal runaway in a transistor refers to

a) high current flow when temperature increases

b) low current flow when temperature increases

c) high current flow when temperature decreases

The correct answer is a Thermal runaway is caused by the 'negative temperature coefficient' of semiconductors. More heat, less resistant, hence more current. More current, more heat etc. etc.

7 When is maximum voltage induced into the rotor of a control synchro transformer?

a) 90 degrees (null position)

b) 0 degrees

c) When spinning fast

The correct answer is b Study a diagram of the control synchro system. Maximum voltage induced in the rotor of the transformer is when the two rotors are at zero degrees to each other

8 Resistors and capacitors are used to couple stages of amplifiers so that

a) only d.c can be applied

b) equal amounts of a.c and d.c can be applied

c) only a.c can be applied

The correct answer is c Same as Question 4. The purpose of the capacitor between amplifier circuits is to block the DC. Hence only AC is fed across the amplifier.

9 An astable multivibrator is a

a) free running vibrator

b) one which requires an input to switch on and off

c) one which requires no input whatsoever

The correct answer is a An astable multivibrator flips on/off continuously providing it has a power supply

10 Op amps use what power supply?

a) 26v a.c

b) 5v - 15v d.c

c) 26v d.c

The correct answer is b Power supplies vary from op-amp to op-amp (manufacturer to manufacturer) but most are +/- 5v to +/- 15v


1 To check the output of a synchro stator it would be preferable to use

a) an Avometer

b) a Valve Voltmeter

c) a Cambridge Bridge

The correct answer is b Since the synchro stator output is a very low voltage, a high impedance multimeter would be used. Since this is not an answer provided (or the CAA guy is probably so old, he has never heard of one) the most sensitive of the three is the Valve Ohmmeter.

2 Synchro capacitors are connected into synchro systems to

a) minimize the torque synchro stator current at null

b) increase the accuracy of the control synchro

c) act as spark suppression due to wear of the slip rings

The correct answer is b Synchro capacitors increase the accuracy of the synchro system

3 The purpose of the fly wheel incorporated in a synchro

a) is to increase the driving force

b) to prevent oscillations

c) to prevent insect ingress

The correct answer is b A flywheel prevents oscillations when used with friction or magnetic braking

4 In a slab desynn transmitter the

a) pick-offs form part of the circuit resistance

b) pick-offs rotate on the slab resister

c) pick-offs are connected to a spark suppressor

The correct answer is b The pick-offs rotate on the slab resistor. Aircraft Electricity and Electronics 5th Edition Eismin Page 352

5 If, in a servo system, the amplitude from the feedback system is below normal, the servo will

a) oscillate

b) be sluggish in operation

c) be overdamped

The correct answer is a The feedback system is designed to prevent overshoot and oscillation (hunting)

6 A desynn instrument has a positive irregular increasing error, you would adjust

a) lever length

b) lever angle

c) lever angle and lever length

The correct answer is b A regular increasing error is an indication of incorrect lever angle.

7 Torque synchro receiver bearing friction will cause

a) hunting

b) misalignment

c) improved accuracy

The correct answer is b Bearing friction will cause the delicate rotor to stop before the desired position

8 A control synchro system pointer is

a) actuated by a permanent magnet

b) displaced by the torque of the stator

c) motor driven

The correct answer is c The receiver of a control synchro is effectively a slow speed synchronous motor

9 A D.C. signal converted to a phase sensitive A.C. is

a) demodulation

b) phase conversion

c) modulation

The correct answer is c DC to phase sensitive AC = 'modulation'

10 If velocity feedback in a servo system is above optimum, this will cause

a) sluggish operation

b) hunting

c) has no effect

The correct answer is a Velocity feedback slows down the operation of the rotor.


1 A device which has a high input impedance, low output impedance and high voltage gain is a

a) Class A amp

b) Class B amp

c) Op-Amp

The correct answer is c This is the definition of an Op-Amp

2 In an integrated circuit, the components are mounted by

a) wires connecting them using conformal coating

b) a three dimensional process with no connections between them required

c) metal oxide film etched onto surface

The correct answer is c All three answers are close to the truth. c) is probably the closest. Aircraft Electricity and Electronics 5th Edition Eismin Page 138

3 For a NPN transistor to conduct the collector circuit has to be

a) more positive than the emitter

b) more positive than the base

c) less positive than the emitter

The correct answer is b Sketch an NPN circuit and mark the two current flows. Aircraft Electricity and Electronics 5th Edition Eismin Page 116

4 The amount of rate feedback from a tachogenerator is

a) proportional to speed

b) inversely proportional to speed

c) constant for all servo speeds

The correct answer is a A tachogenerator provides feedback proportional to its rate (speed)

5 When forward biased, current flow is mainly due to the

a) majority carriers

b) minority carriers

c) germanium bias junction

The correct answer is a Forward bias = majority carriers

6 When forward biased the

a) positive lead is connected to the N type and negative to the P type

b) positive lead is connected to the P type and negative to the N type

c) positive lead is connected to both N and P type

The correct answer is b To forward biased, connect Positive to P, Negative to N. Aircraft Electricity and Electronics 5th Edition Eismin Page 117

7 In a PNP transistor, which way does conventional current flow?

a) Base to emitter

b) Collector to emitter

c) Emitter to Collector

The correct answer is c Sketch a PNP transistor with the two current flows. Mark the directions.

8 In the Zener Diode suppressor shown, point X in respect to point Y should be

a) more negative

b) more Positive

c) either positive or negative

The correct answer is a A Zener Diode is always wired in reverse bias. Aircraft Electricity and Electronics 5th Edition Eismin Page 138

9 In an integrated circuit, the components are inserted

a) manually

b) automatically

c) by doping in successive layers

The correct answer is c An integrated circuit is produced by masking and doping each P and N component successively. Aircraft Electricity and Electronics 5th Edition Eismin Page 121

10 The typical voltage drop across an L.E.D is

a) 2V

b) 4V

c) 6V

The correct answer is a 2V typical


1 In an electronic circuit with an operational amplifier connected in the push-pull configuration, the circuit

a) decreases impedance

b) utilizes both sides of the input signal

c) blocks half of the input signal

The correct answer is b 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.

2 Pin 3 on an op-amp has a + symbol. This designates

a) positive offset null

b) positive input DC pin

c) non-inverting input

The correct answer is c Pin 3 of a 741 Op-Amp (for example) is the non-inverting input

3 An advantage of a FET when compared to a bi-polar transistor is

a) the input resistance is lower

b) the switching time is quicker

c) the input resistance is higher

The correct answer is c A FET has a high input resistance and a low output resistance

4 The semiconductor substrate used in 'chips' is most commonly

a) germanium

b) silicon

c) phiidide

The correct answer is b Silicon is most commonly used

5 Point X compared to point

a) Z is more positive

b) Y is more negative

c) Z is more negative

The correct answer is a NPN transistor. The collector is more positive than the base. Aircraft Electricity and Electronics 5th Edition Eismin Page 116/117

6 The typical bandwidth for an audio frequency amplifier is shown by line

a) X

b) Y

c) Z

The correct answer is a Audio frequency is typically 15Hz - 20 kHz, so X is the closest

7 What control system is used on an input that gives a controlled predetermined output?

a) Open Loop

b) Closed Loop

c) Control Servo

The correct answer is b Only a closed loop control system can give a predetermined output.

8 Increasing velocity feedback from optimum will give

a) sluggish performance

b) faster performance

c) no change on the output

The correct answer is a Velocity feedback is subtracted from the error signal to reduce the rate of the output.

9 A rate control servo system with a steady input voltage will give

a) constant speed

b) increasing speed

c) decreasing speed

The correct answer is a A rate control system with a steady input voltage will give a constant speed output

10 Where are decoupling capacitors used in digital circuits?

a) Between pins 1 & 8

b) Close to the +ve pin

c) Close to the –ve pin

The correct answer is b '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 –ve, especially in DIL packages with more than 8 pins


1 What are the majority carriers for a forward biased PN junction device?

a) Electrons

b) Holes

c) Electrons and holes

The correct answer is c Majority carriers are electrons in the N material, and holes in the P material

2 The resistance measured using an AVO between the Collector and Emitter of a transistor is

a) same both ways

b) smaller Collector to Emitter

c) higher Collector to Emitter

The correct answer is a 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

3 Germanium in its pure state is

a) neutral

b) positively charged

c) negatively charged

The correct answer is a Both germanium and silicon are neutrally charged, even when doped. Aircraft Electricity and Electronics 5th Edition Eismin Page 110

4 Common Collector has the following characteristics

a) Medium Voltage Gain, High Current Gain, Non-Inverted Output b) Low Voltage Gain, High Current Gain, Inverted Output

c) Medium Voltage Gain, Low Current Gain, Inverted Output

The correct answer is a Common collector is a voltage follower, with high current gain

5 Two push-pull transistors have what commoned?

a) Bases

b) Collectors

c) Emitters

The correct answer is c Push-pull transistor configuration has their emitters commoned.

6 In a Common Emitter Amplifier RE is used for

a) biasing

b) stabilisation

c) load control

The correct answer is b The emitter resistor is a stabilizing resistor

7 If the reverse bias voltage across a diode is too high

a) load current increases rapidly

b) load current reverses

c) load current reduces to zero

The correct answer is a If the reverse bias voltage is too high, the diode will break down and pass current.

8 The rotor coil of a synchrotel

a) is stationary

b) rotates

c) rotates only when a current flows in it

The correct answer is a Aircraft Instruments and Integrated Systems Pallett Page 149/150

9 An increase in amplitude of a rate feedback signal will cause

a) sluggish servo operation

b) reduced hunting

c) instable operation

The correct answer is b Rate feedback is to reduce overshoot and oscillation (hunting), therefore, increasing the amplitude (size) of the rate feedback will decrease tendancy to hunt.

10 An increase in negative feedback

a) increases system sensitivity

b) decreases system sensitivity

c) will make the driven device continuously rotate

The correct answer is b Negative feedback (position and/or rate) increases stability but makes the servo unresponsive to small changes.


1 An integrated circuit is manufactured by

a) computer hardware, which use individual circuits on ribbon

b) doping impurities into layers of intrinsic material

c) etching copper tracks onto an insulating board

The correct answer is b ICs are made by doping impurities into intrinsic semiconductor material. Do not confuse with PCBs. Aircraft Electricity and Electronics 5th Edition Eismin Page 138

2 A de-coupling capacitor in a PCB is used to

a) minimise transient currents

b) pass a.c only

c) pass d.c only

The correct answer is b A decoupling capacitor decouples the AC from the DC in a signal, and blocks the DC.

3 A monostable vibrator

a) is switched on by a trigger pulse then within a pre-set time will eventually return to its original state

b) uses a trigger pulse to turn on and the same pulse to turn off

c) uses one pulse to turn on and another to turn off

The correct answer is a A monostable vibrator is switched on by a trigger pulse then within a pre-set time will eventually return to its original state

4 Position feedback is used to

a) ensure control surface moves to the demanded position by the controls

b) to prevent control surface oscillations while the surface is being moved

c) indicate to the pilot the position of the load

The correct answer is a Position feedback is to ensure control surface moves to (and stops at) the demanded position by the controls

5 The output from a control transformer is

a) torque

b) AC voltage

c) DC voltage

The correct answer is b The control transformer provides AC voltage in proportion to the error signal

6 The stator output voltages from a synchro resolver are

a) DC

b) AC single phase

c) 3 phase

The correct answer is b AC single phase from each winding

7 The purpose of synchro capacitors in a differential synchro transmission system

a) to reduce stator current

b) reduce rotor current

c) reduce stator circuit impedance

The correct answer is a Synchro capacitors reduce stator current and make the synchro system more accurate

8 A typical use for resolver synchros is

a) in compass comparitor units

b) engine power instrumentation

c) fly by wire system

The correct answer is a A resolver synchro converts Cartesian coordinates (grid refs) to polar (compass reading) and can be used to check the accuracy of the compass system

9 The purpose of a flywheel in a synchro receiver indicator is to

a) prevent spinning or oscillation

b) encourage spinning

c) increase driving torque

The correct answer is a The flywheel is coupled to some form of brake (e.g. magnetic) to reduce oscillations.

10 A linear variometer is

a) a special synchro giving ac output proportional to shaft angle

b) a special auto transformer for synchro system power supplies

c) an alternative term for a desynn system

The correct answer is a A linear variometer is a device which gives an output voltage directly proportional to angle when coupled to a gyro (for example)


1 In a synchrotel the rotating winding is

a) the stator

b) rotor

c) neither

The correct answer is c Assuming this is a trick question, because a synchrotel has NO rotating winding. Aircraft Instruments and Integrated Systems Pallett Page 149/150

2 The receiver rotor in a torque synchro system oscillates over an arc of approx 75 degrees. The probable cause is

a) short circuit between two stator lines

b) two stator lines reversed

c) one stator line open circuit

The correct answer is c A 'possible' symptom of a stator line open

3 Synchro capacitors are fitted

a) to provide critical damping

b) to make additional damping features unnecessary

c) to improve sensitivity and accuracy

The correct answer is c Synchro capacitors reduce stator current and make the synchro system more accurate

4 The output of a control transformer is made

a) phase and amplitude sensitive by direction and magnitude of the transmitter rotor movement respectively

b) phase and amplitude sensitive by magnitude and direction of the transmitter rotor movement respectively

c) phase sensitive by transmitter rotor excitation and amplitude sensitive by direction of transmitter rotor movement

The correct answer is a Phase provided by TX rotor direction, amplitude provided by TX rotor displacement (magnitude)

5 A transistor is used in

a) current amplifier

b) voltage amplifier

c) both

The correct answer is c A transistor can amplify either current or voltage or both, depending on the configuration (CE, CB, CC)

6 An LED which emits green light uses

a) gallium arsenide phosphide

b) gallium phosphide

c) gallium arsenide

The correct answer is b see http://www.oksolar.com/led/led_color_chart.htm

7 An LED which emits red light uses

a) gallium arsenide phosphide

b) gallium phosphide

c) gallium arsenide

The correct answer is a see http://www.oksolar.com/led/led_color_chart.htm

8 A photodiode is operated under

a) reverse bias conditions

b) forward bias conditions

c) reverse or forward bias conditions

The correct answer is a http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/photdet.html#c2

9 To increase capacitance of a varactor diode

a) reverse bias voltage is increased

b) forward bias voltage is decreased

c) reverse bias voltage is decreased

The correct answer is c http://www.tpub.com/content/neets/14179/css/14179_131.htm

10 Which diode has a lower forward bias voltage?

a) silicon

b) germanium

c) both the same

The correct answer is b Silicon about 0.6V, Germanium about 0.2V. Aircraft Electricity and Electronics 5th Edition Eismin Page 111


1 A Zener diode is used for

a) rectification

b) voltage stabilisation

c) voltage regulation

The correct answer is c A Zener diode is used for voltage regulation. Aircraft Electricity and Electronics 5th Edition Eismin Page 120

2 In the above diagram the phase of the input to the output is

a) in phase

b) 180 degrees out of phase


The correct answer is b A Common Emitter configuration inverts the signal

3 The above diagram shows a

a) voltage doubler

b) half wave rectifier

c) full wave rectifier

The correct answer is a http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/voldoub.html

4 A thyristor SCR is a

a) unidirectional device

b) bi-directional device

c) multidirectional device

The correct answer is a http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/diac.html#c4

5 A bi-directional TRIAC has two SCRs connected in

a) series parallel

b) parallel series

c) inverse parallel

The correct answer is c

6 A thyristor can be forward biased by

a) positive pulse

b) negative pulse

c) positive or negative pulse

The correct answer is a Positive pulse only

7 'N' type materials are doped with

a) acceptors

b) donors

c) acceptors and donors

The correct answer is b 'N' type materials have excess electrons, therefore the impurity element is a donor of electrons. Aircraft Electricity and Electronics 5th Edition Eismin Page 110

8 A junction diode if reverse biased too far, the output will

a) increase

b) stop

c) reverse

The correct answer is a If a reverse bias diode is pushed too far, it will break down and the current will increase. This is the same for normal diodes as it is for zener diodes - but a zener diode will 'reset', a normal diode will be damaged.

9 The input of this circuit will be

a) integrated

b) differentiated

c) logarithmic

The correct answer is a Integrator

10 The most suitable class of amplifier for a radio transmitter is

a) A

b) B

c) C

The correct answer is a Best amplifier is a Class A (if by 'suitable' they mean fidelity - but Class C is most efficient)


1 Under normal operating conditions X will be

a) negative with respect to Z

b) positive with respect to Z

c) negative with respect to Y

The correct answer is b 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

2 What is the base material of a PCB?

a) Insulator

b) Conductor

c) Semiconductor

The correct answer is a Insulator. Aircraft Electricity and Electronics 5th Edition Eismin Page 122

3 What does the output voltage of an op-amp depend upon?

a) The resistors in the circuit

b) The op amp bandwidth

c) The gain of the op-amp

The correct answer is a The output of an op-amp is controlled by the external resistor circuit.

4 In which direction does the current flow on a PNP transistor when forward biased?

a) Emitter to collector

b) Collector to emitter

c) Emitter to base

The correct answer is a PNP, current (conventional) flows emitter to collector

5 What does a resolver do?

a) Resolves a position into sine and cosine components

b) Adds two signals

c) Resolves a movement into sine and cosine components

The correct answer is a A resolver converts a position from polar coordinates into cartesian coordinates, and/or vice versa

6 What component is used to turn AC to DC?

a) Diode

b) Transistor

c) Thyristor

The correct answer is a Although a thyristor (SCR) can be used, a diode is more common. Aircraft Electricity and Electronics 5th Edition Eismin Page 113

7 What is an intrinsic material?

a) One with removed elements

b) One with added elements

c) A pure material

The correct answer is c Intrinsic is a pure material

8 What does the colour of an LED depend upon?

a) Material

b) Voltage

c) Current

The correct answer is a The doping element to be precise. Aircraft Electricity and Electronics 5th Edition Eismin Page 121

9 In an electronic circuit, if the anode of a diode is clamped to ground what is this called?

a) A high level clamp

b) A low level clamping circuit

c) A negative limiting circuit

The correct answer is a Although the terminology used is not known except to the CAA, with the Anode connected to ground, the circuit is a 'Positive Clamper' - closest guess is therefore a)

10 If the feedback is ideal damped, the signal will

a) overshoots once and return back

b) oscillate

c) not overshoot

The correct answer is a Ideal damping is one overshoot


1 The voltage drop of a silicon diode is

a) 0.3 V

b) 0.7 V

c) 1 V

The correct answer is b Aircraft Electricity and Electronics 5th Edition Eismin Page 111

2 The negative feedback for an integrator is connected across a

a) resistor

b) capacitor

c) inductor

The correct answer is b This is referring to an Op-Amp integrator

3 To decrease the capacitance of a varactor

a) forward bias should be increased

b) reverse bias should be decreased

c) reverse bias should be increased


4 In a printed circuit board , the surface resistance testing is

a) the resistance between the tow inductors

b) insulation resistance between adjacent printed conductor

c) between the board and the conductor.

The correct answer is b CAIPs MMC/1-1 para 4.1.7

5 A Zener diode is used across the output for a power supply circuit to

a) give a full wave rectification

b) provide a steady DC voltage output without falling

c) prevent thermal runway

The correct answer is b A Zener diode is the main component in a voltage regulator

6 If a diode has gone open circuit in a full wave bridge rectifier, the output frequency ripple is

a) the same as the input frequency

b) twice the input frequency

c) half the input frequency

The correct answer is a 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.

7 In a tachogenerator the output voltage is

a) inversely proportional to the speed

b) directly proportional to the speed

c) zero

The correct answer is b

8 Resistance - capacitance coupling between amplifiers gives

a) DC

b) AC

c) both


9 Which curve is from a Broadband amplifier?

a) A

b) B

c) C

The correct answer is a

10 To test a diode with a multimeter, the anode lead is placed on the

a) cathode and the positive lead to the anode

b) anode and the negative lead to the cathode

c) cathode and the negative lead to the anode

The correct answer is b Yes, it really did refer to the multimeter's lead as the 'anode lead'


1 A diode is parallel to an LED in an AC circuit to

a) provide correct amount of current for LED when circuit is switched on

b) protect LED from AC current when switched on

c) prevent back EMF in the circuit when LED is switched off

The correct answer is b The negative half cycle of the AC must be bypassed around the LED

2 What type of gate has both inverted inputs and inverted outputs

a) AND gate

b) NAND gate

c) NOR gate

The correct answer is a An AND gate can be made by inverting both the inputs and the output of an OR gate

3 A transistor in Common Emitter mode gives

a) high voltage gain only

b) high current Gain only

c) high power Gain


4 The input resistance to an inverting op-amp is 100 Ohms. The feedback resistance is 100 kilohms. What is the amplifier gain?

a) -1000

b) 1000

c) 1/1000

The correct answer is a Gain = Feedback/input resistance = 100,000/100 = 1000 (minus because it is inverting)

5 For a transistor in common emitter mode, the term Hfe indicates

a) the current gain Ic/Ib at Vce constant

b) the Voltage gain Vce/Vbe at Ib constant

c) the Power gain Pin/Pout


6 In a full wave bridge rectifier

a) the output is pure DC. Frequency is 0 Hz

b) the output voltage is twice the input voltage

c) the output frequency is twice the input frequency

The correct answer is c The output is un-smoothed DC of 2 x input frequency

7 The letter "B" following the identification code on the case of a synchro denotes

a) the modification status

b) that the stator is rotatable

c) that the synchro is second hand

The correct answer is b http://www.tpub.com/content/neets/14187/css/14187_18.htm

8 In a differential amplifier the term 'common mode voltage' means

a) output voltage when both inputs have equal voltages

b) output voltage with non-inverting input at 0 volts

c) output voltage with one input connected to common ground

The correct answer is a http://www.vishay.com/brands/measurements_group/guide/glossary/commodvt.htm

9 In an ideal current amplifier

a) input impedance must be low and output high

b) input impedance must be high and output low

c) both input and output impedances must be low


10 In an ideal voltage amplifier

a) input impedance must be low and output impedance low

b) input impedance must be low and output impedance high

c) input impedance must be high and output impedance low



1

The term Ice related to transistor in common emitter mode means

a) leakage current flowing between Collector and Emitter with Base open circuited

b) forward current between Collector and Emitter with Base connected to ground

c) leakage current between Collector and Emitter with Base connected to ground


2 In a forward biased diode, current is carried by

a) majority carriers

b) minority carriers

c) both

The correct answer is c Forward bias is both, reverse bias is minority carriers only

3 When checking a diode for resistance the positive lead goes to

a) anode and negative lead to cathode

b) cathode and negative lead to anode

c) anode and negative lead to earth

The correct answer is b Presumably they mean reverse bias. Positive lead to cathode

4 In an integrated circuit, active, passive and connecting components are

a) mounted on the outside of the solid block

b) embedded within the solid block

c) connected by fine gold wires

The correct answer is b Hence the term 'integrated circuit'

5 Using Electron flow in a diode the current flows from

a) anode to cathode

b) cathode to Anode

c) cathode to base

The correct answer is b Electron flow is against the arrow direction

6 The primary purpose of rate feedback in a positional servo system is to

a) ensure minimum response time

b) prevent excessive overshoot

c) ensure system linearity


7 In a control surface position indicating system the feedback signal is

a) proportional to the control surface position

b) indirectly proportional to the control surface position

c) in phase with the control surface position


8

a)

b)

c)

9

a)

b)

c)

10

a)

b)

c)

Part 66 Electronic

Documents

correct answer

receiver c

anode c

c proportional

certain voltage c

bthe active element

triac ban scr c

type of semiconductor