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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 elementc) 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 1212 A germanium diode is used for

a) rectificationb) voltage stabilizationc) 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 ACb) So it will work only above a certain voltage

c) So it will work only below a certain voltageThe correct answer is a An LED has a high forward bias voltage drop but is easily damaged when reversebiased. 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 cathodeb) the positive lead of the ohmeter is placed on the anodec) 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 theanode. Note: If the question says 'moving coil meter' then it would be the negative lead on the anode, sincethe negative side of the battery in such a meter is connected to the + lead. Aircraft Electricity and Electronics5th Edition Eismin Page 113

5 In an NPN transistor the P is thea) collectorb) basec) emitter

The correct answer is b NPN or PNP, the middle one is always the Base. Aircraft Electricity and Electronics5th Edition Eismin Page 116

6 The output of a tachogenerator is

a) proportional to speed of rotationb) proportional to positionc) proportional to acceleration

The correct answer is a Read up on tachogenerators

7 AC power is supplied to

a) torque receiver onlyb) torque transmitter onlyc) 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
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b) an SCRc) 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 waxc) By conformal coatingThe correct answer is c Although varnish is often used on PCBs, 'conformal coating' is the name of theprocess 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 transmitterb) 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.

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This is exam number 2. You've been here 1 times.1 Which of the following describes the characteristics of a Thyristor?

a) High voltage handlingb) High current handlingc) 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 materialb) a P type materialc) either an N type or a P type depending on what type of semiconductor material is

usedThe correct answer is a Pentavalent materials make an N type material due to its extra electron. AircraftElectricity 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 impedanceb) Low gain, infinite input Impedance and zero output impedance

c) Infinite gain, infinite input Impedance and zero output impedanceThe correct answer is c Read up on Op Amps

4 How is the amplifier in the diagram shown wired?

a) Common baseb) 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.Ca) ANDb) ORc) NOT

The correct answer is a You must know the Boolean expressions

6 What gate does the following Boolean expression represent

F = A+B+Ca) NOTb) NORc) OR

The correct answer is c You must know the Boolean expressions7 To decrease the voltage gain of a common emitter amplifier you would increase theresistance in the

a) base circuitb) collector circuitc) emitter circuit

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

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8 A resolver has

a) 2 coils on the rotor and 2 coils on the statorb) 3 coils on the rotor and 2 coils on the statorc) 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 area) at 90o to each otherb) 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 impedanceb) high impedancec) current operated

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

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This is exam number 3. You've been here 1 times.1 What type of diode would be used to stop voltage spikes across a coil of a relay?

a) Gunn diode

b) Schottky diodec) Double acting diode

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

2 A silicon diode, when compared to a germanium diode hasa) a higher forward bias voltageb) less forward bias voltagec) the same forward bias voltage

The correct answer is a Si = 0.6V, Ge = 0.2V. Aircraft Electricity and Electronics 5th Edition Eismin Page111

3 A zener diode is used for

a) rectificationb) voltage stabilizationc) 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 sideb) two or more layers on one or both sidesc) 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 dampedb) under dampedc) critically damped

The correct answer is b Get a copy of Pallett's Automatic Flight Control and read up on servos6 The rotor of a desynn indicator is

a) an electromagnetb) a permanent magnetc) an AC magnet

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

7 The posit ion feedback from a potent iometer is

a) anti-phaseb) in phasec) 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 rotorb) single phase stator, 2 phase rotorc) 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 phasec) maximum and anti-phase


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10 A tachogenerator is usually used for

a) rate feedbackb) angular feedbackc) position feedback


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This is exam number 4. You've been here 1 times.

1 What is this circuit?

a) Half wave rectifierb) Full wave rectifier c) Flywheel diode

The correct answer is a Read up on diode applications

2 Differential synchros have

a) a transmitter onlyb) a receiver onlyc) 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 mounteda) by means of wires connecting themb) by metal oxide filmc) 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 diodeb) a triacc) a transistor

The correct answer is a Learn the electronic component symbols. Aircraft Electricity and Electronics 5thEdition Eismin Page 3845 One characteristic of the emitter follower is

a) low resistance outputb) low current amplificationc) high voltage amplification

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

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

a) low servo gainb) instabilityc) 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 onlyb) the rotor windings of both the transmitter and receiverc) the stator windings of the transmitter

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

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

a) 180ob) 90o

c) 0oThe 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 feedbackb) the system will have velocity feedbackc) 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 positionb) obtain a 26 volt AC referencec) add the output of two synchro transmitters

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

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This is exam number 5. You've been here 1 times.1 This is a diagram of a

a) differentiatorb) 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 willa) have no effectb) 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 bothwill have no effect.3 The power supply to a torque synchro system is

a) ACb) DCc) AC or DC

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

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4 This symbol is

a) an LEDb) a laser diodec) a photodiode

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

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

a) the emitter current decreasesb) the collector voltage goes less positivec) 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 isconnected in the

a) common base configurationb) common emitter configurationc) common collector configuration

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

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7 An open loop system is one which has

a) no direct feedback loopb) rate feedback loopc) position feedback only

The correct answer is a Open loop has no feedback.

8 Mechanical friction in a servo results ina) reduced gainb) increased dampingc) increased inertia

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

9 The position feedback signal is

a) in phase with the input demand signalb) in ant i-phase with the demand signalc) 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 dampedb) over dampedc) critically damped

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

This is exam number 6. You've been here 1 times.

1 The power supply to a torque synchro system is connected toa) the transmitter statorb) the transmitter rotor onlyc) 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 thetransmitter rotor, then

a) the transmitter rotor will turn to align with the receiver rotorb) the receiver will overheatc) 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) differentiatorb) integrator c) adder

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

4 A zener diodea) stabilizes voltage at a predetermined level

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b) allows current to flow in one directionc) acts like a switch

The correct answer is a Zener diodes are usually used in voltage regulator circuits. Aircraft Electricity andElectronics 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 currentb) the emitter voltage follows the base voltagec) 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 brushesb) the resistor slabc) 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-phasec) 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 toa) ensure minimum response timeb) prevent excessive overshootc) 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 servomotora) oscillating about a new datumb) 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 constantspeed continually.

10 An E&I bar output at datum hasa) no induced voltage in the secondary windingsb) an imbalance of voltages in the secondary windingsc) equal and opposite voltages induced in the secondary

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

This is exam number 7. You've been here 1 times.1 A non-inverting op-amp

a) has a non-inverting input and an inverting outputb) has an inverting input and a non-inverting outputc) 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 amplifiersb) voltage amplifiers or impedance amplifiersc) 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?

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a) Very high frequency applicationsb) Stabilsationc) Rectification

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

4 The result of cross connecting two of the transmission leads in a torque synchro systemand then turning the rotor of the transmitter 60o clockwise would bea) the receiver would move 60o clockwiseb) the receiver would move 120o anticlockwisec) 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 ofa) constant amplitudeb) variable phasec) variable amplitude, variable phase

The correct answer is c The control windings are fed with variable amplitude AC but the amplitude can bepositive (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 onlyb) the transmitter and receiver rotors onlyc) all three rotors

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

7 A differential synchro rotor hasa) three windingsb) 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 huntsb) high current will flowc) 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, theposition of the receiver rotor will be

a) unchangedb) 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 isa) to overcome the effect of static frictionb) to overcome the effect of viscous frictionc) 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) whensystem is switched off.

This is exam number 8. You've been here 1 times.1 When removing a microprocessor

a) no damage is done by static discharge

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b) considerable damage can be done by static dischargec) 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 thea) common base configuration

b) common emitter configurationc) common collector configurationThe correct answer is b Only the common emitter configuration provides both current and voltage gaingreater than 1.

3 How do you increase voltage gain of an amplifier?

a) decrease base circuit biasb) decrease input resistancec) 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) 120oc) 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 abrake is used. The brake is

a) applied during trimming to prevent oscillations about the demand positionb) applied when trimming is complete to prevent stabilizer creepc) 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 coilb) three coils at 120oc) two coils at 90o


7 In a control synchro the stator current ceases to flow whena) the CT rotor is at nullb) when the two rotors are alignedc) when power is removed

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

8 In a speed control servo system (rate control), the purpose of the tachogenerator isa) to make the velocity proportional to servo demandb) to make the deflection proportional to servo demandc) 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 isthat the rotor position

a) is unchangedb) is changed by 120oc) is changed by 180o


10 The rotor of a torque synchro indicator isa) supplied with an excitation voltageb) short circuited

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c) connected in series with the transmitter stator coil

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

This is exam number 9. You've been here 1 times.1 When a hole diffuses from a p-region to the n-region it

a) becomes a minority carrier in the n-regionb) 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 dotb) clockwise from the dotc) from left to right from the dot

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

3 To increase the output of a servo amplifier, it is necessary toa) reduce the tacho feedbackb) increase the tacho feedbackc) increase the position feedback

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

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

a) 0o, 180ob) 90o, 270o

c) 90o, 120o

The correct answer is b Read up on induction motors.

5 a two phase induction motor used in a servomechanisma) will always require a starterb) is self starting under light loadsc) 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 willa) vary its speed with input error voltageb) have a constant speed for any given input voltagec) 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 characteristicsb) good speed/voltage relationshipc) 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 otherb) the TX and TR rotors are 90o to each otherc) 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.

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9 Reversal of two of the stator connections on a torque synchro receiver would causea) the transmitter to become the receiverb) the output to move the same direction as the inputc) the output to move the reverse direction to the input


10 An AC tachogenerator stator hasa) two windings 180o apartb) three windings 120o apartc) two windings 90o apart

The correct answer is c Read up on the tachogenerator.

This is exam number 10. You've been here 1 times.1 A junction diode

a) has one p-n junctionb) 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 EditionEismin Page 111

2 When the rotor of an AC tachogenerator is stationary, the rotor hasa) no circulating currentsb) low circulating currentsc) no magnetic fields

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

3 The output of a tachogenerator should bea) sinusoidal

b) exponentialc) 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 motora) moves to a certain positionb) moves at a constant speedc) 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 servomechanisma) must only have position feedbackb) must have both position and velocity feedbackc) can have either position or velocity feedback

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

6 Critical damping in a servomechanism isa) the point which allows just one overshoot before the load comes to restb) the amount of damping that results in the load just not oscillatingc) 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 anyovershoot.

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

a) transmitter rotor and amplifierb) receiver rotor and amplifier c) transmitter and receiver rotors

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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 bya) connections between the transformer rotor and the amplifier reversedb) connections to the transmitter rotor reversedc) 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 feedbacka) opposes the demand inputb) assists the demand inputc) 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 bya) introduction of an integratorb) keeping the error detector (summing point) output as low as possiblec) decreasing the coulomb friction in the system

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

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This is exam number 11. You've been here 1 times.1 The junction barrier offers opposit ion to only

a) holes in the p-regionb) 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 movesb) increase the speed the load movesc) have no effect on speed

The correct answer is a Velocity feedback opposes demand input therefore it reduces thew speed the loadmoves.3 A two phase motor will stop when

a) the reference phase is reversedb) the control phase is reversed

c) the control phase is zeroThe 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 voltageb) variable voltage, constant frequencyc) variable frequency, variable voltage

The correct answer is b A tachogenerator output is the same frequency as the input (i.e. constant) but thevoltage varies.5 Rate feedback can be obtained from a

a) synchrob) tachogenerator

c) potentiometer

The correct answer is b A tachogenerator produces rate feedback.6 Positional feedback can be obtained from a

a) synchrob) 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) stictionb) coulomb frictionc) 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 otherb) 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).

For full explanations of all these questions, and for many more new and up-to-date questions, with

correct answers, full explanations, downloadable material and Tutorial Support, please visit


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

a) moving 25o clockwise

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b) moving 25o anticlockwisec) moving 180o to rectify the defect

The correct answer is b Cross connecting two stator leads of a control synchro will make the magnetic fieldin 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 inertiab) the mechanism is heavy and has high inertiac) 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 highinertia.

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This is exam number 12. You've been here 1 times.1 Reverse bias

a) lowers the potential barrierb) raises the potential barrier

c) greatly increases the majority carrier currentThe correct answer is b Read up on semiconductor theory.

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

a) motor would run in the wrong directionb) input signal to the amplifier would reducec) system would tend to oscillate

The correct answer is c Feedback from the tachogenerator prevents overspeed and overshoot, sodisconnecting 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 responsec) reduces tendency to hunt

The correct answer is b Increasing servo-amplifier gain will make the system respond faster but will alsocause it to overshoot and oscillate (hunt).4 In a control synchro the stator current ceases to flow when the

a) CT rotor is at nullb) two rotors are alignedc) power is removed

The correct answer is c In a control synchro current flows in the stator lines at all times, regardless of theposition of the tarnsformer rotor.5 The term 'velocity lag' refers to a

a) speed errorb) position error c) acceleration error

The correct answer is b Velocity lag is the difference between the demand input and the load position. It istherefore a position error.6 The rotor of an AC tachogenerator

a) has skewed slotsb) has a copper, brass or aluminium cylinderc) rotates at constant speed

The correct answer is b An AC generator rotor is made from a diamagnetic material such as copper, brassor aluminium.7 A servo system with transient negative velocity feedback

a) is damped with little velocity lagb) is damped with high velocity lagc) is underdamped with high velocity lag

The correct answer is a Transient velocity feedback is a variable feedback which can be switched on whenthe system is about to overshoot (and anticipates the overshoot). But it can also be switched off when it isnot 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 phaseb) reverse the polarity of both the control phase and reference phasec) shift the reference by 90o

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

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9 In a rate servo (speed control) the signal into the servo amplifier isa) input voltage plus tachogenerator outputb) input voltage minus tachogenerator outputc) input voltage plus position feedback voltage

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

10 Loss of DC to a servo amplifier causes the motor toa) run continuouslyb) stopc) reverse

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

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This is exam number 13. You've been here 1 times.1 Avalanche breakdown occurs when

a) forward current becomes excessiveb) forward bias exceeds a certain valuec) reverse bias exceeds a certain value

The correct answer is c Reverse biasing a diode will cause avalanche breakdown at a certain value. AircraftElectricity 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) rectifierb) 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 thecorrect 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 ratec) 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 requiredb) accuracy is of limited importance but robust construction and reliability is

importantc) 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 thedirection of movement.

5 A low frequency sinusoidal input will cause a closed loop servomechanism load toa) move to a demand position with no overshootb) move backwards and forwards at the input frequencyc) 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 demandposition with no or minimal overshoot.

6 To reduce oscillations about a demand positiona) the amount of velocity feedback would be decreasedb) the amount of velocity feedback would be increasedc) 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 andthe 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 thereb) the load would move to a new position, proportional to the drift and then return

back to the datum positionc) 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 willmove 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 thedemand voltage

a) only when the load is slowing down

b) at all times when the load is movingc) only when the load is speeding up or slowing downThe correct answer is c Automatic Flight Control EHJ Pallett Page 91.

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9 Positive feedback applied to a servomechanism

a) decreases the response of the systemb) opposes the demand signalc) 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 rotorb) two windings at 90o apartc) three windings at 120o apart


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This is exam number 14. You've been here 1 times.1 A differential synchro transmitter used for addition has

a) the TDX S1 and S3 connections cross connected to the TXb) the TDX S1 and S3 connections cross connected to the TRc) 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 ofthe 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 fora relatively small increase in voltage occurs

a) only after the forward bias exceeds the potential barrierb) when the flow of minority carriers is sufficient to cause an avalanche breakdownc) 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 voltageexceeds 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 movementc) 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 toa) allow the coil to energize with only one polarityb) cause a delay in switching onc) 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 therelay coil de-energises. Aircraft Electricity and Electronics 5th Edition Eismin Page 121

5 Differential transmitters are used to

a) add or subtract two electrical signalsb) add or subtract a mechanical signal to an electrical synchro signalc) 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 anelectrical signal derived from the synchro transmitter.

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

a) reverse the reference phase supplyb) change over two rotor and stator connectionsc) change over all three stator windings

The correct answer is b To convert a differential synchro from subtraction to addition you must swap two ofthe rotor leads AND swap two of the rotor leads.7 What is resistor R used for?

a) Amplificationb) Biasc) Stabilisation

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

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8 When resolving a Cartesian input to a Polar outputa) the inputs are a shaft angle and a voltageb) the outputs are two voltagesc) 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 thepositive terminal is put to the

a) anodeb) cathodec) either anode or cathode

The correct answer is a To forward bias a diode with a multimeter, the positive lead must be connected tothe anode. Note: If it were a moving coil meter, you must connect the negative lead to the anode since thepositive end of the battery is connected to the negative lead.10 A resolver synchro output is obtained from a rotor with

a) one single coilb) 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.

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This is exam number 15. You've been here 1 times.1 The input and output signals of a common emitter amplifier are

a) equalb) out of phasec) in phase

The correct answer is b The common emitter amplifier is the only configuration which provides an outputwhich is anti-phase with the input.2 The output of a resolver synchro is

a) dependant upon the position of the rotor onlyb) proportional to the speed of input rotationc) 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 thedistance.

3 The rotor of an autosyn position indicating system isa) a permanent magnetb) 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 frequenciesa) above the frequency required onlyb) below the frequency required onlyc) 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 isa) a dc electromagnetb) 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 thea) stator current is highb) stator current is lowc) rotor current is high

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

7 Torque synchro systems are normally used when thea) mechanical load is low

b) mechanical load is highc) 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) 90ob) 120oc) 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 coreb) damps the pointer oscillations

c) is of a value of 800 Hz

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The correct answer is c A signal from the permanent magnet flux is induced every time the soft iron comesout 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 fieldb) in the same direction as the primary fieldc) 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 statorcoils produce a magnetic field which opposes the field in the rotor which created it. (Similar to the secondaryfield of a transformer).

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This is exam number 16. You've been here 1 times.1 The cogging effect in synchros is rectif ied by

a) using carbon brushesb) using an elliptical cogc) 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 whena) no signal is applied to the inputb) it is unbiasedc) 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 thetransistor. No signal is applied.

3 In an unbiased p-n junction, current flow isa) due to the diffusion of minority carriers onlyb) zero, because no charges are crossing the junctionc) 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 synchrosystem would

a) cause a 180o displacement between the transmitter and the receiverb) have no effect on the indication, but would cause a heavy current to flowc) 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 a180 degree displacement of the receiver rotor.

5 Torque synchro systems are normally used when thea) mechanical load is lowb) mechanical load is highc) 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 regionb) the base is n-type materialc) 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) Transmitterb) Transducer c) Transponder

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

8 Which way does conventional current flow in a PNP junction?a) Collector to emitterb) Emitter to basec) Collector to base

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

9 Electrical power is supplied to a synchro rotor

a) directly

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b) through slip ringsc) 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 toa) increase the driving force

b) prevent oscillationsc) prevent insect ingress

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

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

a) are equal and oppositeb) is maximumc) is zero

The correct answer is a Since an EandI bar transformer secondary winding is wound in series opposition, atdatum 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 degreesb) 80 degreesc) 90 degrees

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

10 In a synchrotel, thea) rotor coil is fixed and the stator coil movesb) rotor coil and stator coil is fixedc) stator coil is fixed and the rotor coil moves

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

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This is exam number 18. You've been here 1 times.1 On a PCB, a decoupling capacitor is used to get rid of transient currents between whichpoints?

a) The electronic circuit and the aircraft groundb) 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 rectifierb) 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 materialb) The electronsc) 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 ofa) an N type materialb) a P type materialc) a C type material

The correct answer is a An atom with five electrons in its outer shell (pentavalent) will provide an extra freeelectron and make the material an N type. Aircraft Electricity and Electronics 5th Edition Eismin Page 1105 In a FET, the junct ion connections are called

a) drain, source and gateb) 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 andElectronics 5th Edition Eismin Page 1206 In the Boolean algebra statement below, the gate described is

F = A.B.Ca) Nandb) 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 outputwaveform?

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a) Shottkyb) Gunnc) Zener

The correct answer is a The first part of the device is a basic RC differentiator, providing positive andnegative pulses from the square wave input. The diode blocks the negative pulses. Since the amplitude issmall, 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 stabilityb) decreases amplifier stabilityc) has no effect

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

9 How is a push-pull transistor arrangement connected?a) emitter to emitterb) 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 bya) excessive heat causing maximum current flowb) excessive heat causing minimum current flowc) low heat causing minimum current flow

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

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This is exam number 19. You've been here 1 times.1 A single integrated circuit Op Amp has how many pins?

a) 4b) 7c) 8

The correct answer is c Inverting and non-inverting input, output, positive and negative supply, two offsetnull connections (for a potentiometer) plus one leg not used = 8. Aircraft Electricity and Electronics 5thEdition Eismin Page 1402 What is the output of the amplifier shown below?

a) 0Vb) 3Vc) 5V

The correct answer is c A basic adding op-amp. 4 + 0 + 1 = 53 A thyristor is commonly used for

a) voltage regulationb) overvolts regulationc) 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) zenerb) 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 excessiveb) forward bias exceeds a certain valuec) 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 area) anode, cathode, sourceb) source, drain, gatec) gate, cathode, anode

The correct answer is c The electrodes of an SCR are the anode, cathode and the gate. Aircraft Electricityand Electronics 5th Edition Eismin Page 1207 What gives an LED its colour?

a) A gasb) 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 isa) fwd biasedb) reverse biased

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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 beforward biased. Aircraft Electricity and Electronics 5th Edition Eismin Page 1169 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 itis with an NPN transistor).

10 Infinite gain, infinite input impedance & zero output impedance is characteristic of aa) Class A ampb) Class B ampc) Op amp

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

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This is exam number 20. You've been here 1 times.1 Forward voltage of a silicon diode is

a) 0.6Vb) 0.2Vc) 1.6V

The correct answer is a Si = 0.6V, Ge = 0.2V Aircraft Electricity and Electronics 5th Edition Eismin Page111 or 113

2 An advantage of a common emitter isa) it is a voltage followerb) it has high power gainc) 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) Ab) Bc) C

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

For full explanations of all these questions, and for many more new and up-to-date questions, withcorrect answers, full explanations, downloadable material and Tutorial Support, please visit


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

a) High resistance one wayb) High resistance both waysc) 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 PNPas NPN). Aircraft Electricity and Electronics 5th Edition Eismin Page 119

5 What is the typical volts drop across an LEDa) 1.6Vb) 0.2Vc) 0.4V

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

6 What diode gives off l ight photons when forward biaseda) LEDb) Shottky diodec) 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 havea) one of 2 states of logic outputb) 2 or more outputsc) an analogue output

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

8

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This is a diagram ofa) an SCRb) a transistor c) a photo diode

The correct answer is c Learn the electronic component symbols. Aircraft Electricity and Electronics 5thEdition Eismin Page 3859 In a synchro, what is used to convert signals from one form to another?

a) Transmitterb) Transducer c) Transformer

The correct answer is b A 'transducer' converts one signal type to another. Aircraft Electricity and Electronics5th Edition Eismin Page 171

10 Components on an integrated circuit are

a) in the solidb) don't need themc) on the surface

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

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This is exam number 21. You've been here 1 times.1 What diode is used to stop power spikes in a coil?

a) Two directional zener diodeb) Shottky diodec) Gunn diode

The correct answer is a A two directional zener diode (actually 2 zener diodes back-to-back) is used to stoppower 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 conductingb) reverse biased not conductingc) forward biased conducting

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

3 Using electron flow in a diode the current flows froma) Anode to Cathode

b) Cathode to Anodec) Cathode to Base

The correct answer is b ELECTRON FLOW (i.e. American notation) is cathode to anode (against the arrowdirection). Aircraft Electricity and Electronics 5th Edition Eismin Page 1114 A control surface position feedback signal is

a) proportional to surface positionb) inversely proportional to surface positionc) non-linear

The correct answer is a Position feedback is proportional to surface position. Meaning, as control surfacedeflection increases, so does the feedback.5 In a PNP transistor, conventional current will flow when

a) the emitter is more positive than the baseb) the base is more positive than the emitterc) 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 toan NPN).6 An E&I transformer out of datum has

a) equal and opposite voltages in each windingsb) unequal and opposite voltages in both windingsc) 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 feedbackb) velocity feedbackc) positional feedback

The correct answer is c Presumably they are referring to a 'position gyro' (as in artificial horison anddirectional gyro) and not a 'rate gyro' (as in the slip indicator). The latter would make a) nad b) correctanyway 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 90ob) in phasec) 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

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a) in phaseb) out of phasec) 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 regiona) it becomes a minority carrier in the n regionb) 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).

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This is exam number 22. You've been here 1 times.1 A junction diode

a) has one p-n junctionb) is similar to a vacuum diode but cannot rectifyc) can handle only small currents

The correct answer is a A junction diode is so named for its one junction. Aircraft Electricity and Electronics5th Edition Eismin Page 111

2 A germanium diode is used for

a) voltage stabilisationb) rectificationc) signal detection

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

3 A germanium diode

a) has a lower forward bias voltage than a silicon diodeb) 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. AircraftElectricity and Electronics 5th Edition Eismin Page 1114 a VLSIC has

a) less than 1000 gatesb) more than 1000 gatesc) more than 10,000 gates

The correct answer is b VLSIC = Very Large Scale Integrated Circuit (> 1,000 gates). Aircraft Electricity andElectronics 5th Edition Eismin Page 1385 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 1c) 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 inputa) RSb) JKc) 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 parallelb) a capacitor in parallel and an inductor in seriesc) 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 Electricityand Electronics 5th Edition Eismin Page 1438 When you use an op amp as a buffer it has

a) high input impedance and low output impedanceb) low input impedance and high output impedancec) 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 2889 What switches off a thyristor?

a) Remove the gate voltageb) Remove supply voltagec) Reverse bias gate

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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 12010 When an SCR is switched on it has

a) high resistanceb) low resistance

c) no change in resistanceThe correct answer is b An SCR is basically a switch, which, when switched on has a low resistance. AircraftElectricity and Electronics 5th Edition Eismin Page 120

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This is exam number 23. You've been here 1 times.1 What is required for the switching of a monostable multivibrator

a) one trigger pulse to switch on and another to switch offb) 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 anexternal trigger pulse is applied, the circuit moves from its permamnent stable state then drops back after ashort while.2 A transistor at saturation has

a) high resistanceb) low resistancec) 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 stageb) 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) inphaseb) 90 degrees out of phasec) 180 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 producingphotons?

a) gunnb) 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 SCRa) positiveb) negativec) 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) Additionb) Subtractionc) 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 putb) The circuit has 2 stable states and will stay in both at the same timec) 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 voltageb) below its breakdown voltage

c) either above or below its breakdown voltage

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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 12010 A JFET is

a) voltage sensitiveb) current sensitivec) 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. AircraftElectricity and Electronics 5th Edition Eismin Page 119

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This is exam number 24. You've been here 1 times.1 A triac is a type of

a) thyristorb) thermistor c) transistor

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

2 A piece of pure Germaniuma) has a deficit of electronsb) is electrically stablec) has an excess of electrons

The correct answer is b In a solid piece of semiconductor material, all the valence electrons are occupied inthe covalent bond. It does not conduct electricity. Aircraft Electricity and Electronics 5th Edition Eismin Page110

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

a) cease to flow

b) increasec) reverse direction

The correct answer is b If a junction diode is reverse biased too far, it will 'breakdown' and a high current willflow.4 An RC connected amp has

a) no AC acrossb) no DC acrossc) 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. Henceonly AC is fed across the amplifier5 When a PN junction is forward biased, it conducts via

a) majority carrierb) minority carrier c) intrinsic carrier

The correct answer is a Forward biased - majority carriers6 Thermal runaway in a transistor refers to

a) high current flow when temperature increasesb) low current flow when temperature increasesc) high current flow when temperature decreases

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

For full explanations of all these questions, and for many more new and up-to-date

questions, with correct answers, full explanations, downloadable material and Tutorial Support, please visithttp://www.club66pro.co.uk

7 When is maximum voltage induced into the rotor of a control synchro transformer?a) 90 degrees (null position)b) 0 degreesc) When spinning fast

The correct answer is b Study a diagram of the control synchro system. Maximum voltage induced in therotor of the transformer is when the two rotors are at zero degrees to each other8 Resistors and capacitors are used to couple stages of amplifiers so that

a) only d.c can be appliedb) equal amounts of a.c and d.c can be appliedc) only a.c can be applied

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

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9 An astable multivibrator is a

a) free running vibratorb) one which requires an input to switch on and offc) 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.cb) 5v - 15v d.cc) 26v d.c

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

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This is exam number 25. You've been here 1 times.1 To check the output of a synchro stator it would be preferable to use

a) an Avometerb) 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 multimeterwould be used. Since this is not an answer provided (or the CAA guy is probably so old, he has never heardof 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 nullb) increase the accuracy of the control synchroc) act as spark suppression due to wear of the slip rings

The correct answer is b Synchro capacitors increase the accuracy of the synchro system3 The purpose of the fly wheel incorporated in a synchro

a) is to increase the driving forceb) to prevent oscillations

c) to prevent insect ingress

The correct answer is b A flywheel prevents oscillations when used with friction or magnetic braking4 In a slab desynn transmitter the

a) pick-offs form part of the circuit resistanceb) pick-offs rotate on the slab resisterc) 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 5thEdition Eismin Page 3525 If, in a servo system, the amplitude from the feedback system is below normal, the servowill

a) oscillate

b) be sluggish in operationc) 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 adjusta) lever lengthb) lever anglec) 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) huntingb) misalignmentc) 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 magnetb) displaced by the torque of the statorc) 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) demodulationb) phase conversion

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

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

a) sluggish operationb) huntingc) has no effect

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

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This is exam number 26. You've been here 1 times.1 A device which has a high input impedance, low output impedance and high voltage gain is a

a) Class A ampb) Class B ampc) 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 coatingb) a three dimensional process with no connections between them requiredc) 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 Electricityand Electronics 5th Edition Eismin Page 138

3 For a NPN transistor to conduct the collector circuit has to bea) more positive than the emitterb) more positive than the basec) less positive than the emitter

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

4 The amount of rate feedback from a tachogenerator is

a) proportional to speedb) inversely proportional to speedc) 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 carriersb) minority carriersc) 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 typeb) positive lead is connected to the P type and negative to the N typec) 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 andElectronics 5th Edition Eismin Page 117

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

a) Base to emitterb) Collector to emitter c) Emitter to Collector

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

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

a) more negativeb) more Positivec) either positive or negative

The correct answer is a A Zener Diode is always wired in reverse bias. Aircraft Electricity and Electronics 5thEdition Eismin Page 1389 In an integrated circuit, the components are inserted

a) manuallyb) automaticallyc) by doping in successive layers

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

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

a) 2Vb) 4Vc) 6V

The correct answer is a 2V typical

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This is exam number 27. You've been here 1 times.1 In an electronic circuit with an operational amplifier connected in the push-pull configuration, thecircuit

a) decreases impedanceb) 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 theoutput, 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 nullb) positive input DC pinc) 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 lowerb) 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 commonlya) germaniumb) siliconc) phiidide

The correct answer is b Silicon is most commonly used

5 Point X compared to point

a) Z is more positiveb) Y is more negativec) Z is more negative

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

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

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a) Xb) Yc) 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 Loopb) Closed Loopc) 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 performanceb) faster performancec) 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 speedb) increasing speedc) 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 & 8b) Close to the +ve pinc) Close to the ve pin

The correct answer is b 'Close' is an important requirement. The capacitor has to be as close as possible tothe +ve power supply pin. Answer a) could also be true assuming pin 8 to be ground, but in the real worldnot all pin 8s are ve, especially in DIL packages with more than 8 pins

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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 operationb) reduced huntingc) instable operation

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

10 An increase in negative feedback

a) increases system sensitivityb) decreases system sensitivityc) will make the driven device continuously rotate

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

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This is exam number 29. You've been here 1 times.1 An integrated circuit is manufactured by

a) computer hardware, which use individual circuits on ribbonb) doping impurities into layers of intrinsic materialc) etching copper tracks onto an insulating board

The correct answer is b ICs are made by doping impurities into intrinsic semiconductor material. Do notconfuse with PCBs. Aircraft Electricity and Electronics 5th Edition Eismin Page 138

For full explanations of all these questions, and for many more new and up-to-date questions, with

correct answers, full explanations, downloadable material and Tutorial Support, please visit


2 A de-coupling capacitor in a PCB is used toa) minimise transient currentsb) pass a.c onlyc) 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 returnto its original state

b) uses a trigger pulse to turn on and the same pulse to turn offc) 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 timewill eventually return to its original state

4 Position feedback is used toa) ensure control surface moves to the demanded position by the controlsb) to prevent control surface oscillations while the surface is being movedc) 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) thedemanded position by the controls

5 The output from a control transformer is

a) torqueb) AC voltagec) 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) DCb) AC single phasec) 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 currentb) reduce rotor current

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c) reduce stator circuit impedance

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

8 A typical use for resolver synchros is

a) in compass comparitor unitsb) engine power instrumentationc) fly by wire system

The correct answer is a A resolver synchro converts Cartesian coordinates (grid refs) to polar (compassreading) 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 oscillationb) encourage spinningc) 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 angleb) a special auto transformer for synchro system power suppliesc) 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 toangle when coupled to a gyro (for example)

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This is exam number 30. You've been here 1 times.1 In a synchrotel the rotating winding is

a) the statorb) 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 probablecause is

a) short circuit between two stator linesb) two stator lines reversedc) 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 dampingb) to make additional damping features unnecessaryc) to improve sensitivity and accuracy

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

4 The output of a control transformer is made

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

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

movement respectivelyc) 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 amplifierb) voltage amplifier c) both

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

6 An LED which emits green light uses

a) gallium arsenide phosphideb) gallium phosphidec) 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

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b) gallium phosphidec) 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 conditionsb) forward bias conditionsc) 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 increasedb) forward bias voltage is decreasedc) 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) siliconb) germaniumc) both the same

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

This is exam number 31. You've been here 1 times.1 A Zener diode is used for

a) rectificationb) voltage stabilisationc) voltage regulation

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

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

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a) in phaseb) 180 degrees out of phasec) 90 degrees out of phase

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

3 The above diagram shows a

a) voltage doublerb) 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 deviceb) bi-directional devicec) 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 ina) series parallelb) parallel seriesc) inverse parallel

The correct answer is c

6 A thyristor can be forward biased bya) positive pulseb) negative pulsec) positive or negative pulse

The correct answer is a Positive pulse only

7 'N' type materials are doped with

a) acceptorsb) donorsc) acceptors and donors

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

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

a) increaseb) stopc) reverse

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

9 The input of this circuit will be

a) integratedb) differentiatedc) logarithmic

The correct answer is a Integrator

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

a) Ab) Bc) C

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

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This is exam number 32. You've been here 1 times.1 Under normal operating conditions X

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