AC/DCPREGUNTAS

• 1) A component consuming 80 watts at 8 amps would require a supply of:• A) 0.008 kV • B) 5 Volts • C) 0,01 kV • D) 100 Volts

• 2) In an aeroplane utilising a constant frequency AC power supply, DC power is obtained from a:• A) rotary converter. • B) 3 phase current transformer unit. • C) Transformer Rectifier Unit. • D) static inverter.

• 3) Aircraft standard fuses are fitted to:• A) DC circuits only. • B) AC circuits. • C) protect wiring in battery circuits only. • D) DC and AC circuits.

• 4) A 24V, 60 Ah battery is driving a 48 Watts light bulb. Approximately how long would the battery last assuming that it is new?

• A) 120 hours. • B) 2,5 hours. • C) 60 hours. • D) 30 hours.

• 5) Two resistors with values of 6 Ohm and 100 Ohm are connected in parallel. Their combined resistance is:• A) 106 Ohm. • B) 5,66 Ohm. • C) 94 Ohm. • D) 0,177 Ohm.

• 6) Magnetism can be used to generate electricity by converting mechanical energy to electrical energy by:• A) electro motive force. • B) electro magnetic conversion. • C) electro magnetic induction. • D) electro self induction.

• 7) The operating principle of a fuse is:• A) a high resistance metal wire. • B) a relay. • C) a bimetallic strip. • D) a wire with a predetermined melting point.

• 8) Bonding is used to protect the aircraft against fire by:• A) maintaining a different electrical potential throughout the aircraft's structure. • B) providing an earth return system. • C) provision of an independent ignition system. • D) ensuring the same electrical potential of all metal components in the aircraft's structure.

• 9) If the power being drawn by a resistor is 100 watts from a 50V supply, what is the resistance of the load?• A) 4 Ohms. • B) 50 Ohms. • C) 25 Ohms. • D) 2 Ohms.

• 10) The commutator of a DC generator converts:• A) AC to DC • B) DC to AC • C) AC to AC at a different voltage • D) DC to AC at a different voltage

• (Refer to figure 021-12)11) In the following diagram A, B and C are respectively the:

• A) battery master switch, starter switch, starter relay. • B) starter relay, starter switch, battery master switch. • C) battery master switch, starter relay, starter switch. • D) starter switch, battery master switch, starter relay.

• 12) Recharging an aircraft's battery from an AC system would require:• A) a rectifier. • B) a TRU. • C) nothing since the battery can supply AC as well. • D) an inverter.

• 13) A rotary valve actuator is in the closed position. Its 'OPEN' limit switch is... and its 'CLOSE' limit switch is...• A) closed, closed • B) open, open • C) closed, open • D) open, closed

• 14) When a battery is almost fully discharged there is a tendency for the:• A) voltage to increase due to the current available. • B) current produced to increase due to the reduced voltage. • C) voltage to decrease under load. • D) electrolyte to " boil" .

• 15) With regards to a light aircraft electrical system, where is the generator switch normally located?• A) In series with the armature. • B) In parallel with the field winding. • C) In series with the field winding. • D) In series with the cut-out switch.

• 16) The purpose of a battery protection unit is generally to isolate the battery: • from the bus when the battery charge is deemed satisfactory • when there is a battery overheat condition • in case of an internal short circuit • in case of a fault on the ground power unit• The combination which regroups all of the correct statements is :• A) 1, 2, 3 • B) 1, 2, 3, 4 • C) 1, 2 • D) 1

• 17) In order that DC generators will achieve equal load sharing when operating in parallel, it is necessary to ensure that:• A) equal loads are connected to each generator busbar before paralleling. • B) the synchronising bus-bar is disconnected from the busbar system. • C) adequate voltage differences exists. • D) their voltages are almost equal.

• 18) The power dissipated as heat by a resistance R with an applied voltage V carrying a current I can be expressed as:• A) V x V / I. • B) I x I / V. • C) I x R x R. • D) I x I x R.

• 19) Aircraft systems are almost always:• A) single pole static systems • B) earth return with static system emergency back up • C) dipole systems • D) earth return systems

• 20) An aircraft has total services drawing 120 amps, essential services drawing 45 amps and vital services drawing 5 amps. The designer has 50 Ah capacity batteries (at system voltage) available and wishes to ensure that the aircraft can fly safely for at least 2 hours following a breakdown of electrical generators. What configuration of batteries would be employed?

• A) 6 in parallel. • B) 3 in series. • C) 3 in parallel. • D) 2 in parallel.

• 21) Impedance is:• A) the combined effect of power factor and phase angle. • B) the combined effect of real and imaginary power. • C) the combined effect of resistance and conductivity. • D) the combined effect of resistance and reactance.

• 22) Consider a battery voltage V, connected to R1 and R2 which are in parallel: If V is 250 volts, R1 is 500 Ohms but R2 is a very low resistance then:

• A) R2 is insignificant. • B) A large total current will flow. • C) The total current from the battery will approximate the current in R1. • D) A small total current will flow.

• 23) A generator is taken Off-line by:• A) operating the field switch • B) removing all loads • C) creating a short circuit. • D) manual operation of the generator cut-out

• 24) Electrical batteries when connected in parallel provide... amp/hr capacity and... voltage.• A) increased; reduced • B) reduced; increased • C) the same; increased • D) increased; the same

• 25) The international symbol of electrical power is• A) P and it is measured in watts. • B) I and it is measured in amperes. • C) R and it is measured in ohms. • D) U and it is measured in volts.

• 26) The capacity of a battery is expressed in terms of:• A) volts. • B) ampere-hours. • C) internal resistance. • D) watts.

• 27) A 12 volt battery that has 1 dead cell:• A) has its capacity reduced by 1/12th. • B) is unserviceable. • C) still has a voltage of 12V. • D) has less capacity.

• 28) When an electrical circuit is open circuited:• A) resistance will be zero • B) resistance will be high • C) components will operate normally • D) resistance will be low

• 29) The unit of inductance is:• A) the Ohm. • B) the Henry. • C) the Reactance. • D) the Farad.

• 30) The inductance of several inductors connected in series can be calculated to be:• A) the sum of the individual inductances divided by the number of inductors. • B) the inverse of the sum of the inverses of the individual inductances. • C) the sum of the individual inductances. • D) the inverse of the sum of the individual inductances.

• 31) The purpose of the voltage regulator is to:• A) Keep a constant frequency • B) Keep a constant power output from the generator • C) Keep a constant voltage output from the generator • D) Keep a constant current output from the generator

• 32) What unit is used to measure potential difference between two points in an electrical circuit?• A) Ohm • B) Coulombs • C) Amps • D) Volts

• 33) True power is measured in:• A) Kilojoules. • B) Kilowatts. • C) Kilovolt-amperes. • D) Kilovolt-amperes-reactive.

• 34) When fully charged, what is the maximum voltage across a lead-acid cell?• A) 2 volts. • B) 12 volts. • C) 24 volts. • D) 2.2 volts.

• 35) In a supply system which is AC, DC requirements are provided by:• A) rotary inverter. • B) batteries. • C) TRU's. • D) a static inverter.

• 36) In normal conditions, generator output voltage is arranged to be:• A) less than battery voltage • B) as high as possible • C) exactly the same as battery voltage • D) higher then battery voltage

• 37) An ammeter indicates a high rate of charge after engine start. This...• A) is dangerous. The field circuit breaker should be tripped manually. • B) is dangerous. The engine should be shut down immediately. • C) indicates generator failure. • D) is only allowed for a short period.

• 38) Fuses are rated to a value by:• A) their resistance measured in ohms • B) the number of volts they will pass • C) their wattage • D) the number of amperes they will carry

• 39) The connection in series of two 12 volt / 40 amp hours batteries, will create a unit with the following characteristics:• A) 24 volt / 80 amp hours • B) 24 volt / 40 amp hours • C) 12 volt / 40 amp hours • D) 12 volt / 80 amp hours

• 40) Usually, in conductive materials:• A) the resistance increases with increasing temperature. • B) resistance and temperature are not related. • C) the resistance remains constant regardless of temperature. • D) the resistance decreases with increasing temperature.

• 41) When carrying out battery condition check using the aeroplane’ s voltmeter:• A) the load condition is unimportant. • B) a load should be applied to the battery in order to give a better indication of condition. • C) no load should be applied to the battery because it would depress the voltage. • D) the battery should be isolated.

• 42) The total current flow in an electrical circuit with resistors in parallel is equal to...• A) the sum of all the currents in all the components divided by the number of components. • B) the sum of all the currents in all the components in the circuit. • C) the reciprocal of the sum of the current reciprocals. • D) the sum of all the current reciprocals.

• 43) What are fuses rated in?• A) Watts. • B) Volts. • C) Amps. • D) Ohm.

• 44) Apparent Power is measured in:• A) KWR or WR. • B) KW or Watts. • C) KVAR of VAR. • D) KVA or VA.

• 45) An aircraft electrical circuit which uses the aircraft structure as a return path to earth, may be defined as a• A) single pole circuit • B) double pole circuit • C) semi-negative system • D) complete negative system

• 46) Voltage is proportional to rate of change of current in a:• A) battery. • B) capacitor. • C) inductor. • D) resistor.

• 47) In a DC generator circuit the reverse current relay:• A) allows current to flow in both directions through the generator. • B) prevents the battery from motoring the generator at low speeds and when stationary. • C) allows the charge rate to drop as the battery becomes charged. • D) prevents the battery from too high a charging rate.

• 48) Voltage is:• A) is also known as potential difference • B) a measure of the power gained • C) a measure of the electrical charge passing a point • D) an electro motive force

• 49) The difference in electrical potential in a circuit is measured in:• A) Watts. • B) Joules. • C) Volts. • D) Amperes.

• 50) When does a generator cut-out open?• A) When generator voltage exceeds battery voltage. • B) When battery voltage exceeds a certain level. • C) When battery voltage exceeds generator voltage. • D) When generator voltage exceeds a certain value.

• 51) On a self-exited DC generator, if the voltage regulator increases the current through the field windings then:• A) The intensity of the field increases and the output voltage increases. • B) The intensity of the field decreases and the output voltage decreases. • C) The intensity of the field increases and the output voltage decreases. • D) The intensity of the field decreases and the output voltage increases.

• 52) The capacity of a typical lead acid battery for aviation use is• A) 12-18 Ah. • B) 24 V. • C) 12 Volts • D) 4-8 Ah.

• 53) The power in a direct current circuit is equal to:• A) I x R • B) V x R • C) V x I • D) R x I x V

• 54) The total current in a parallel circuit is equal to:• A) the sum of all the currents of all the components in the circuit • B) the sum of the current reciprocals • C) the reciprocal of the sum of the current reciprocals • D) the sum of all the currents of all the components, divided by the number of components

• 55) Voltage is a measure of:• A) resistance to current. • B) potential differential. • C) current. • D) coulombs per joule.

• 56) The voltage regulator of a DC generator is connected in:• A) in series with the armature and in parallel with the shunt field. • B) parallel with the armature and in parallel with the shunt field. • C) series with the armature and in series with the shunt field. • D) parallel with the armature and in series with the shunt field.

• 57) A simple circuit has 4 amps flowing through a 5 ohm resistor. How much power is being used?• A) 80 watts. • B) 60 watts. • C) 20 watts. • D) 100 watts.

• 58) The connection in parallel of two 12 volt / 40 amp hours batteries, will create a unit with the following characteristics:• A) 12 volt / 80 amp hours • B) 24 volt / 80 amp hours • C) 24 volt / 40 amp hours • D) 12 volt / 40 amp hours

• 59) The capacitance of several capacitors connected in series is equal to:• A) the inverse of the sum of the inverses of the individual capacitances. • B) the sum of the individual capacitances divided by the number of capacitors. • C) the sum of the individual capacitances. • D) the inverse of the sum of the individual capacitances.

• 60) An Electromotive Force (EMF) can be measured with:• A) a Hall effect probe. • B) a voltmeter. • C) an ammeter. • D) an ohmmeter.

• 61) A spill of electrolyte from a NiCad battery onto someone's skin should be:• A) rinsed with water and add sodium bicarbonate • B) rinsed with a weak acid (e.g. boric acid). • C) rinsed with a weak alkali (e.g. potassium hydroxide) • D) rinsed with a concentrated acid (e.g. sulphuric)

• 62) Resistance is expressed in... and the basic SI units for it are...• A) Ohms, R • B) Ohms, J/C • C) Farad, F • D) Ohms, V/A

• 63) Voltmeters and ammeters usually indicate:• A) RMS values. • B) mean values. • C) peak-to-peak values. • D) amplitudes.

• 64) Current is expressed in... and the basic SI units for it are...• A) Amperes, kg/s • B) Amperes, C/s • C) Farad, A/s • D) Coulombs, A/s

• 65) Batteries are rated in:• A) Joule • B) Henry • C) Ampere hours and Volts • D) Volts

• 66) Which unit is commonly used for reactive power?• A) kWR. • B) kVAR. • C) kW. • D) kVA.

• 67) What is the purpose of a battery cut-out?• A) to open when the battery is fully charged. • B) to prevent the battery discharging to the bus-bar when the generator is on-line. • C) to prevent the battery discharging into the generator. • D) to connect the battery to the starter motor when starting the engine.

• 68) The so called HOT BUSSES or DIRECT BUSSES are:• A) providing an alternative current • B) automatically connected to the battery if generators have failed • C) kept in operating conditions by an electrical resistance in the case of energy failure • D) directly connected to the battery

• 69) On an aircraft with an earth return electrical system:• A) the static electricity is discharged through a chain linkage dangled from the ram air turbine under emergency conditions • B) one lead of all electrical components is earthed and the other is connected to the bonding system • C) one lead of the battery and one lead of the electrical components are connected to the aircraft structure • D) the static electricity is discharged through the tyres on landing

• 70) The type of windings commonly used in DC starter motors are:• A) series wound. • B) shunt wound. • C) series shunt wound. • D) compound wound.

• 71) Consider a battery voltage V, connected to four resistors R1, R2, R3, R4. They are connected as two pairs in parallel (R1 and R2, R3 and R4). The two pairs are connected in series: If R1 and R2 are both 8 Ohms, R3 is 6 Ohms, R4 is 3 Ohms, the total resistance of the circuit is:

• A) 6.16 Ohms. • B) 5.33 Ohms. • C) 25 Ohms. • D) 6 Ohms.

• 72) Consider a battery voltage V, connected to three resistors R1, R2, R3. R2 and R3 are in parallel with one another, and the combination of them is in series with R1. If R1 is 2 Ohms and has 6 volts across it, R2 has 2 amps running through it and R3 is 6 Ohms, what is R2?

• A) 6 Ohms. • B) 3 Ohms. • C) Impossible to tell without also knowing total current from the battery. • D) Impossible to tell without knowing V.

• 73) When refuelling an aircraft:• A) the refuelling nozzle must be bonded to the fuel tank. • B) there is no fire risk as both the bowser and aircraft are bonded by the refuelling nozzle. • C) the continuity between nozzle and hose must be infinity. • D) the bonding plug must be connected to the earth terminal.

• 74) An aircraft has three batteries, each of 12 volts with a 40 Ah capacity, connected in series. The resultant unit has:• A) a capacity of 120 Ah and a voltage of 12 volts. • B) a voltage of 36 volts and a capacity of 40 Ah. • C) a voltage of 36 volts and a capacity of 120 Ah. • D) a voltage of 24 volts and a capacity of 80 Ah.

• 75) The output voltage of DC generators used in aircraft is normally regulated by:• A) Controlling the current in the armature (anker) windings • B) Varying the RPM of the generator • C) Varying the torque applied to the generator • D) Controlling the current in the field windings

• 76) Which of the following statements best describes two resistors connected in parallel?• A) Resistors should never be connected in parallel. • B) The combined resistance is always less than the smallest individual resistance present. • C) The combined resistance is equal to the average of the individual resistances. • D) The combined resistance is always greater than the largest individual resistance present.

• 77) What is the purpose of a voltmeter?• A) to measure current. • B) to measure potential difference and is measured in parallel with the component. • C) to measure potential difference and is fitted in series with the load. • D) to measure voltage and is fitted in series with the component.

• 78) When being charged, the specific gravity of the electrolyte in a Ni-cad cell:• A) decreases. • B) increases. • C) depends on the voltage applied. • D) exhibits little change.

• 79) A current limiter fuse in a DC generation system is used to:• A) limit the current in the field circuit • B) limit the current in the armature • C) instantaneously rupture to limit the current in the load • D) allow a short term overload before rupturing

• 80) Voltage is proportional to charge on:• A) an inductance. • B) a capacitor. • C) a battery. • D) a resistor.

• 81) DC generators are rated in:• A) kVAR. • B) kWA. • C) kVA. • D) kW.

• 82) Obvious disadvantages using Lead-Acid batteries in airplanes are:• A) They have insufficient capacity and is volume and weight inefficient. • B) They only carry 12 volt, and most modern airplanes use 24 volt circuits. • C) They are expensive compared to other batteries used in airplanes. • D) The Lead-Acid battery is too heavy.

• 83) The purpose of protecting a circuit against excessive current conditions is:• A) to prevent battery run down when a generator has failed • B) to prevent a reverse current causing failure of the equipment • C) to prevent deterioration and failure of the aircraft's wiring and switch gear by excess heat. • D) to provide a means of controlling and distributing the current in a circuit

• 84) An aircraft has 3 navigation lights, each rated at 24 watts, which are connected in parallel and supplied by a 12 volts battery. What would be the total current that the battery has to deliver to the navigation lights circuit?

• A) 1,5 Amperes. • B) 0,5 Amperes. • C) 2 Amperes. • D) 6 Amperes.

• 85) It may be determined that an aircraft is not properly bonded if:• A) a circuit breaker pops out. • B) static noises can be heard on the radio. • C) there is interference on the VOR receiver. • D) there is heavy corrosion on the fuselage skin mountings.

• 86) When two DC generators are operating in parallel, control of load sharing is achieved by:• A) an equalising circuit which, in conjunction with the voltage regulators, varies the field excitation current of the generators. • B) carrying out systematic load-shedding procedures. • C) an equalising circuit which, in turn, controls the speed of the generators. • D) the synchronous bus-bar.

• 87) Consider a battery voltage V, connected to four resistors R1, R2, R3, R4. They are connected as two pairs in parallel (R1 and R2, R3 and R4). The two pairs are connected in series: If R1 is twice R2, R3 is half R4, and the current in R1 is 9 amps, the current in R4 is:

• A) 3 amps. • B) 4.5 amps. • C) 9 amps. • D) 18 amps

• 88) Two 0.03 Henry inductors are placed in series. The resulting inductance is:• A) 0,015 H. • B) 0,09 H. • C) 0,06 H. • D) 0,03 H.

• 89) An aircraft has a battery with a capacity of 60 Ah. Assuming that it will provide its normal capacity and is discharged in 10 hours:

• A) it will deliver 60 amperes for 10 hours • B) it will deliver 4.8 amperes for 10 hours • C) it will deliver 6 amperes for 10 hours • D) it will deliver 60 amperes for 1 hour

• 90) What efficiency is required in order for a battery to pass a capacity test?• A) 90% • B) 60% • C) 50% • D) 80%

• 91) The purpose of bonding is:• A) to keep all parts of the aircraft at the same potential. • B) to protect against lightning strikes. • C) to prevent static electrical charges building up. • D) to keep the aircraft at zero potential.

• 92) Consider a battery voltage V and two resistors (R1 and R2) which are connected in series: If R1 is 2 ohms, R2 has 3 amps through it and 3 volts across it what is V?

• A) Impossible to tell without knowing R2. • B) At most, 3 volts. • C) 6 volts. • D) 9 volts.

• 93) During normal cruise flight conditions a Ni-Cd battery's ammeter shows a high rate of charge. What does this indicate?• A) that a high demand is being made on the system • B) that the generator should be disconnected from the bus bar • C) that a possible thermal runaway exists • D) it can be ignored as it is quite normal

• 94) When a centre zero ammeter is reading to the left:• A) the generator is supporting the system. • B) no current is flowing. • C) the battery is discharging to the generator. • D) the battery is discharging to the system.

• 95) A circuit breaker:• A) may be reset manually after the fault has been rectified. • B) can be reset on the ground only. • C) is self resetting after the fault has been rectified. • D) can only be reset after major maintenance.

• 96) The voltage of a fully charged lead-acid battery cell is:• A) 2,2 V • B) 1,2 V • C) 1,8 V • D) 1,4 V

• 97) A battery is made up of 5 NiCad cells, each having a voltage of 1.2V and a capacity of 20Ah, connected in series. What is the resulting combination?

• A) 12 V, 20Ah. • B) 6 V, 100Ah. • C) 30 V, 100Ah. • D) 6 V, 20Ah.

• 98) 1 ampere equals:• A) 1,000,000 milliamps • B) 1,000,000 millicoulombs per second • C) 1,000 microamps • D) 1,000 milliamps

• 99) The advantages of grounding the negative pole of the aircraft structure are: • Weight saving • Easy fault detection • Increase of short-circuit risk • Reduction of short-circuit risk • Circuits are not single-wired lines• The combination regrouping all the correct statements is :• A) 2, 3, 5 • B) 1, 2, 4 • C) 1, 2, 3 • D) 1, 3, 5

• 100) A 12 volt battery is connected to a 24 watt light bulb. The battery lasts for 10 hours. What is the battery capacity?• A) 20 Ah. • B) 5 Ah. • C) 240 Wh. • D) 120 Vh.

• 101) 8 volts are applied to a 2 Ohm resistor. What current will flow?• A) 4 coulombs. • B) 6 coulombs per second. • C) 4 amps. • D) 24 watts.

• 102) In a multi engined aircraft, how are the ammeters usually arranged?• A) One for each load bus bar. • B) One for each generator. • C) One for each set of generators which are paralleled. • D) One for all generators.

• 103) If you double the EMF, you will:• A) halve current. • B) double resistance. • C) double power. • D) double current.

• 104) When a conductor cuts the flux of a magnetic field:• A) the field will collapse • B) an electromotive force (EMF) is induced in the conductor • C) current will flow in accordance with Flemings left hand rule • D) there will be no effect on the conductor

• 105) Electrical power is expressed in:• A) Coulombs • B) Volts • C) Watts • D) Amperes

• 106) A Ni-cad cell is fully charged. Its on load voltage is:• A) 1,2 volts. • B) 12 volts. • C) 2,2 volts. • D) 24 volts.

• 107) An earth return electrical system has:• A) one lead to the service and one lead to the structure • B) two leads from the system to each service • C) two leads from the system to the structure • D) two leads from each service to the aircraft's structure

• 108) The capacitance of several capacitors connected in parallel can be calculated to be:• A) the sum of the individual capacitances divided by the number of capacitors. • B) the inverse of the sum of the individual capacitances. • C) the inverse of the sum of the inverses of the individual capacitances. • D) the sum of the individual capacitances.

• 109) Parallel wound motors produce a... starting torque and their speed varies... with load.• A) high, moderately • B) moderate, only very slightly • C) high, slightly • D) low, significantly

• 110) The voltage regulator of a DC generator:• A) maintains a constant voltage • B) ensures a reverse current flow when the electrical circuit is broken • C) increases voltage when engine RPM increases • D) is used to limit generator voltage only when the engine is over speeding

• 111) R1 and R2 resistances are connected in parallel. The value of the equivalent resistance (Req) so obtained is given by the following formula:

• A) 1/Req = 1/R1 + 1/R2 • B) 1/Req = 1/(R1 + R2) • C) Req = R1 + R2 • D) Req = R1 x R2

• 112) In aeronautics, the most commonly used batteries are NiCad because...• A) their electrolyte is neither corrosive nor dangerous • B) they weigh less than lead-acid batteries • C) they are cheaper than lead-acid batteries • D) their output voltage is more constant than lead-acid batteries

• 113) The difference in electrical potential between two points in a circuit is measured in:• A) Amperes. • B) Volts. • C) Watts. • D) Coulombs.

• 114) Assume a constant speed DC generator providing a constant output voltage. If the electrical load increases, the voltage regulator will:

• A) maintain the intensity of the excitation current constant. • B) change the direction of the excitation current. • C) decrease the intensity of the excitation current. • D) increase the intensity of the excitation current.

• 115) The purpose of an inverter could be:• A) all answers are correct. • B) to provide emergency power to essential AC consumers from a battery bus bar. • C) to supply DC power when the battery is out of service. • D) to convert DC into AC.

• 116) In a circuit containing reactive elements, the total current:• A) may be out of phase with the voltage. • B) will be independent of voltage. • C) must be in phase with voltage. • D) must be out of phase with the voltage.

• 117) An ammeter measures:• A) potential differences. • B) Coulombs per second. • C) power dissipated. • D) Amps per second.

• 118) A 12 volt battery has a rating of 24 Ah. If fully charged, how long can it supply current to a 12 volt, 24 watt bulb?• A) 1 hour. • B) 12 hours. • C) 6 hours. • D) 48 hours.

• 119) Which of the following is an appropriate substance to use to neutralise the electrolyte from a Nicad cell?• A) A concentrated solution of sodium bicarbonate. • B) A dilute solution of sodium bicarbonate. • C) A dilute solution of boric acid. • D) Lead sulphate in powdered form.

• 120) If one of the 12 cells of a lead-acid battery is dead, the battery:• A) has 1/12 less capacity, but can still be used. • B) has 1/12 less voltage, but can still be used. • C) is unserviceable. • D) has 1/12 less voltage and less capacity, but can still be used.

• 121) What is load shedding?• A) distributing of the load between generators • B) reduction of the total loads • C) a reduction of the voltage in the system • D) an increase in the current to services

• 122) The voltage regulator of a DC generator is connected in:• A) series with the shunt field coil. • B) parallel with the armature. • C) series with the armature. • D) parallel with the shunt field coil.

• 123) A 12 volt lead acid battery has a broken connection in a cell, the battery:• A) is unserviceable • B) provides 1/12th less voltage for the same time • C) will suffer from thermal runaway • D) provides 1/12th less voltage for 1/12th less time

• 124) On board present aircraft, the batteries used are-mainly Nickel-Cadmium. Their advantages are: • low risk of thermal runaway • high internal resistance, hence higher power • good charging and discharging capability at high rating • wider permissible temperature range • good storage capability • sturdiness owing to its metal casing • the electrolyte density remains unchanged during charging• The combination of correct statements is:• A) 3, 4, 6, 7 • B) 3, 4, 5, 6 • C) 1, 2, 5, 6, 7 • D) 2, 3, 4, 5, 6

• 125) When approaching discharge, the characteristics of a battery are as follows:• A) voltage decreases, internal resistance decreases • B) voltage decreases, internal resistance increases • C) voltage decreases, internal resistance unchanged • D) voltage decreases, internal resistance increases, especially with Ni-cads

• 126) The primary purpose of bonding the metallic parts of an aeroplane is to:• A) prevent electrolytic corrosion between mating surfaces of similar metals. • B) isolate all components electrically and thus make the static potential constant. • C) provide a single earth for electrical devices. • D) provide safe distribution of electrical charges and currents.

• 127) A bus-bar is:• A) the stator of a moving coil instrument. • B) a device which may only be used in DC circuits. • C) a device permitting operation of two or more switches together. • D) a distribution point for electrical power.

• 128) The detection of a feeder fault on a direct current circuit results in: • automatic disconnection of the generator from the aircraft AC busbar • opening of generator field current relay • opening of the main relay of the generator breaker • opening of balancing circuit connecting two generators • lighting of an indicator lamp• The combination of correct statements is:• A) 1, 3, 5 • B) 2, 3, 4, 5 • C) 1, 2, 3, 4, 5 • D) 2, 4, 5

• 129) When being charged the specific gravity of the electrolyte in a lead-acid cell:• A) depends on current flow. • B) increases. • C) decreases. • D) exhibits little change.

• 130) A 3 microfarad capacitor is in parallel with a 6 microfarad capacitor. What is the combined capacitance?• A) 9 microfarads • B) 3 microfarads • C) 4.5 microfarads • D) 2 microfarads

• 131) 12.5 watts are being consumed by a 2 Ohm resistor. What voltage has been applied?• A) Impossible to tell without knowing the current. • B) 3.125 volts. • C) 5 volts. • D) 6.25 volts.

• 132) The on-load voltage of a lead-acid battery is... and is measured using...• A) 2.2 Volts, Capacity meter. • B) 1.35 Volts, battery charger. • C) 1.2 Volts, Voltmeter. • D) 2 Volts, Voltmeter.

• 133) A component that provides 115 VAC output after an input of 28 VDC is called:• A) A rotary transformer. • B) An inverter, static or rotary. • C) A static rectifier. • D) A transformer / rectifier unit.

• 134) A 2 Ohm resistor has 3 amps through it. What power is being consumed by the resistor?• A) 18 watts • B) 2 watts • C) 4.5 watts • D) 18 joules per second

• 135) Resistors in series act as..., resistors in parallel act as...• A) voltage dividers, voltage subtractors. • B) current subtractors, voltage dividers. • C) current dividers, current subtractors. • D) voltage dividers, current dividers.

• 136) Consider a battery voltage V, connected to three resistors R1, R2, R3. R2 and R3 are in parallel with one another, and the combination of them is in series with R1. If R1 is 3 Ohms, R2 is 10 Ohms and R3 is 5 Ohms, what is the total resistance of the circuit?

• A) 7.31 Ohms. • B) 6.33 Ohms. • C) 18 Ohms. • D) 1.58 Ohms.

• 137) In an electrical circuit with 28V, 7A and 4ohms, the dissipated power is equal to:• A) 196 Volts • B) 113 Watts • C) 196 Watts • D) 28 Watts

• 138) If the frequency of the supply in a series capacitive circuit is increased, the current flowing in the circuit will:• A) decrease. • B) remain the same. • C) be zero. • D) increase.

• 139) Overloading an electrical circuit causes the fuse to blow. This:• A) disconnects the fuse from its holder. • B) fractures the fuse case. • C) melts the fuse link wire. • D) bends the bimetallic strip out of position.

• 140) One essential law of magnetism is:• A) The distance between the poles does not affect the amount of attraction between poles. • B) Equal poles attracts each other and unequal poles repel each other. • C) A permanent magnet bar will always have a north and a south pole. • D) Magnetic power equals the product of current and voltage.

• 141) There is a maximum amount of flux which can be carried by a piece of ferromagnetic material. This is due to:• A) saturation • B) high coercivity • C) residual magnetism • D) energy loss due to hysteresis

• 142) Electrical services are connected in parallel. When some are switched off:• A) current stays the same • B) current decreases • C) current may increase or decrease, depending on battery internal resistance • D) current increases

• 143) Voltage is expressed in... and the basic SI units for it are...• A) Volteres, C/J • B) Volts, J/C • C) Tension, C/J • D) Emf, J/C

• 144) Switching a DC alternator off is achieved by:• A) Close circuiting the electromagnet. • B) Open circuiting the field electromagnet. • C) Open circuiting the armature. • D) Close circuiting the armature.

• 145) The SI unit used for measuring... is...• A) EMF, Amperes. • B) current, Volts. • C) resistance, Ohms. • D) energy, Watts.

• 146) What type of electrical circuit is usually protected using a current limiter?• A) DC circuits only • B) Logic circuits • C) High duty power distribution circuits • D) Low duty power distribution circuits

• 147) Consider a battery voltage V, connected to three resistors R1, R2, R3. R2 and R3 are in parallel with one another, and the combination of them is in series with R1. If R2 is twice R3 and has 2 amps running through it, the power consumed by R3 is 16 watts, V is 12 volts, what is the power consumed by R1?

• A) 48 watts. • B) 72 watts. • C) 24 watts. • D) Impossible to tell without knowing either R1 or R2.

• 148) What is the purpose of an ammeter?• A) to measure current when fitted in series in the circuit • B) to measure resistance • C) to measure current when fitted in parallel in the circuit • D) to measure emf when fitted in series with the component

• 149) If a DC circuit with a total resistance of 2 Ohms has 12 volts DC applied, then the resulting current is:• A) 24 A. • B) 0,167 A. • C) 6 A. • D) 10 A.

• 150) Consider a battery voltage V, connected to R1 and R2 which are in parallel: If V is 12 volts and R1 is 4 Ohms, what current is flowing through R2?

• A) Impossible to tell, but must be at most 3 amps. • B) Impossible to tell without further information. • C) 3 amps. • D) Impossible to tell, but must be at least 3 amps.

• 151) When AC generators are operated in parallel, they must be of the same:• A) voltage and amperage. • B) amperage and kVAR. • C) voltage and frequency. • D) frequency and amperage.

• 152) The oil system of an IDG will be:• A) the same as the main hydraulic aircraft system. • B) independent of all other IDG's and independent of the hydraulic system. • C) drawn from a common reservoir shared by all engines and IDG's. • D) drawn from a common reservoir shared by all IDG's.

• 153) Typical aircraft AC system run on:• A) 50 Hz, 115 volts. • B) 400 Hz, 115 volts. • C) 400 Hz, 250 volts. • D) 50 Hz, 24 volts.

• 154) A unit that converts electrical DC into AC is:• A) a thermistor • B) an inverter • C) a transformer rectifier unit • D) an AC generator

• 155) When loaded, an induction motor:• A) runs at less than synchronous speed. • B) can run at any speed, depending upon the applied load. • C) can run at any speed, depending on the applied voltage. • D) runs at exactly synchronous speed.

• (Refer to figure 021-15)156) Which of this circuit diagram symbols represents an auto-transformer?

• A) B. • B) C. • C) A. • D) D.

• 157) What is the purpose of a load sharing circuit?• A) To achieve the same output frequency before paralleling • B) Shed all unnecessary loads automatically • C) Control the alternators in parallel in order that each one takes a fair and equal share of the load • D) To achieve identical voltage outputs on all generators

• 158) The main purpose of a Constant Speed Drive unit is to:• A) maintain a constant frequency. • B) take part in the balancing of reactive loads. • C) take part in the voltage regulation. • D) mechanically protect the alternator drive shaft during coupling.

• 159) In a three phase star connected power system, to calculate phase voltage from line voltage:• A) Phase voltage is the same as line voltage in a three phase star connected power system. • B) Uline = sqrt (3) x Ufase in a three phase star connected power system. • C) Ufase = sqrt (3) x Uline in a three phase star connected power system. • D) The result depends on the phase angle difference.

• 160) A short circuit on a single pole electrical circuit could be caused by:• A) the component supply being in contact with the aircraft's structure. • B) the battery negative lead becoming disconnected in flight. • C) the component earth connection earthed to the aircraft's structure. • D) the supply to a component being disconnected.

• 161) A CSD unit which has been disconnected in flight:• A) automatically resets in flight providing engine rpm is below a given value. • B) may be reset on the ground only, after engine shut-down. • C) automatically resets at engine shut-down. • D) may be reset in flight using the reset mechanism.

• 162) If the supply frequency to an inductor is decreased, the reactance... and the current...• A) increases, decreases. • B) increases, increases. • C) decreases, increases. • D) decreases, decreases.

• 163) In a parallel AC supply system, the load is measured in:• A) kW / kVAR. • B) kW / kW. • C) kW / kVA. • D) kW / kV.

• 164) The output frequency of an AC generator depends on:• A) generator RPM and number of pole pairs. • B) generator RPM and number of phases. • C) generator RPM.. • D) generator RPM, number of pole pairs and number of phases.

• 165) A rectifier is a unit that• A) transforms one Ac-voltage to a greater / smaller AC-voltage. • B) produces a DC output from AC input. • C) prevents rectified current from occurring in the electrical system. • D) protects the electrical system from over voltages induced in the system itself.

• 166) The reason for using inverters in an electrical system is.• A) To change the DC voltage. • B) To change DC into AC. • C) To change AC into DC. • D) To avoid a short circuit.

• 167) If a circuit breaker trips, which of the following actions is acceptable?• A) Under no circumstance attempt to replace it • B) Allow it to cool then make one attempt only to reset it • C) Reset to a lower value only • D) Immediately reset it

• 168) On an earth return aircraft wiring circuit:• A) the positive pole is connected to the aircraft's structure. • B) the negative pole is connected to the aircraft's structure. • C) a second cable carries the return. • D) the negative pole is connected to the positive pole.

• 169) The purpose of static wick dischargers is to:• A) be able to fly higher because of less electrical friction. • B) dissipate static charge of the aircraft in-flight thus avoiding radio interference as a result of static electricity. • C) dissipate static charge from the aircraft skin after landing. • D) provide a path to ground for static charges when refuelling.

• 170) In a frequency wild AC supply system, a constant frequency can be derived:• A) from a TRU. • B) from the APU. • C) from an inverter. • D) from frequency wild generator maintained at constant engine RPM.

• 171) When an underspeed fault is detected on an AC generator connected to the aircraft AC busbar, the protection device opens:

• A) exciter breaker • B) generator breaker • C) exciter breaker, generator breaker and tie breaker • D) exciter breaker and generator breaker

• 172) The output voltage of a transformer is twice as high as the input voltage. The transformation ratio is:• A) 2 • B) 50 • C) depends on the number of turn of wire in the primary and secondary windings. • D) 1/2

• 173) To convert from an RMS value to an amplitude it is necessary to:• A) multiply the RMS value by 2 • B) multiply the amplitude by 2 • C) multiply the RMS value by 1 • D) divide the RMS value by 0,707

• 174) The speed of an asynchronous four-pole motor fed at a frequency of 400 Hertz is:• A) 1600 revolutions per minute. • B) 12000 revolutions per minute. • C) 800 revolutions per minute. • D) 6000 revolutions per minute.

• 175) A star connected three phase generator can be used for:• A) single phase equipment only. • B) all multiphase equipment. • C) single phase and/or three phase equipment. • D) three phase equipment only.

• 176) Reversing two phases of a three phase motor will:• A) cause the motor to reverse its direction of rotation. • B) have no effect on the motor. • C) cause the motor to stall and stop. • D) cause the motor to overheat and burn out.

• 177) The purpose of a CSDU is to:• A) maintain constant supply frequency. • B) maintain a constant generator output voltage. • C) ensure a constant mechanical load on the engine. • D) prevent the generator from overspeeding.

• 178) The rectification of a three phase supply can be effected by using a formation of... rectifiers in a bridge circuit.• A) 4 • B) 6 • C) 2 • D) 3

• 179) A 3 phase AC generator has 3 separate stator windings spaced at:• A) 60° . • B) 120° . • C) 45° . • D) 90° .

• 180) A carbon pile voltage regulator:• A) is not present on a shunt wound self excited DC generator. • B) is only used when paralleling generators. • C) compresses the carbon pile if the generator output voltage is too high. • D) reduces the compression of the carbon pile if the generator output voltage is too high.

• 181) Generator paralleling through busbars is done to assure that:• A) wiring is done properly, and so that we easily can detect errors in the system. • B) all consumers receive the same generator voltage. • C) different consumers can be fed from different sources. • D) the biggest generator gets the highest load.

• 182) The most commonly used circuit protection device in modern aircraft is a• A) fuse. • B) resistor. • C) push and pull circuit breaker. • D) current limiter.

• 183) Electrical bonding of an aircraft is used to: • protect the aircraft against lightning effects. • reset the electrostatic potential of the aircraft to a value approximating 0 volt • reduce radio interference on radio communication systems • set the aircraft to a single potential• The combination regrouping all the correct statements is:• A) 1, 3, 4 • B) 3, 4 • C) 1, 2, 3 • D) 2, 4

• 184) When loaded, a synchronous motor:• A) runs at less than synchronous speed. • B) runs at exactly synchronous speed. • C) can run at any speed, depending on the applied voltage. • D) can run at any speed, depending upon the applied load.

• 185) Static electricity in an aircraft is a fire hazard because:• A) excessive voltage on screening cables could cause arcing through insulation. • B) metal components overheat and could ignite flammable materials. • C) aircraft tyres could become charged and burst. • D) sparks are produced which could ignite flammable materials.

• 186) A brushless AC generator output is tapped:• A) From the stator. • B) From the rotor. • C) By slip rings instead. • D) By a commutator instead.

• 187) When a persistent over excitation fault is detected on only one AC generator, the protection device opens the:• A) tie breaker. • B) exciter breaker, generator breaker and tie breaker. • C) generator breaker and tie breaker. • D) exciter breaker and generator breaker.

• 188) When AC generators are operated in parallel:• A) Real loads must be balanced. • B) Both real and reactive loads must be balanced. • C) Reactive loads must be balanced. • D) Neither need be balanced.

• 189) A star wound generator, can provide how many different voltage(s):• A) 2. • B) Unlimited. • C) 3. • D) 1.

• 190) The purpose of static wick dischargers is to:• A) prevent static charges from building up in flight only. • B) eliminate radio interference. • C) reduce fire hazard during refuelling only. • D) discharge static electricity on landing.

• 191) On starting, in a brushless AC generator with no commutator rings, the generator is activated by:• A) the stabilizer winding jointly with the voltage regulator. • B) the main field winding. • C) a set of permanent magnets. • D) the auxiliary winding.

• 192) In a solely inductive circuit, what is the relationship between current and voltage?• A) Current lags voltage and is inversely related to frequency. • B) Current leads voltage and is proportional to frequency. • C) Current lags voltage and is proportional to frequency. • D) Current leads voltage and is inversely related to frequency.

• 193) Can frequency wild AC generators be operated in parallel?• A) Never. • B) Only if the engines are running at the same speed. • C) In an emergency, to supply services for a limited time at risk of causing further damage. • D) Always.

• 194) In flight, if the constant speed drive (CSD) temperature indicator is in the red arc the:• A) pilot has to throttle back. • B) pilot must disconnect it and manually control the alternator. • C) pilot must disconnect it, and the generator is not available for the rest of flight. • D) pilot can disconnect it to allow it to cool and use it again.

• 195) A " trip-free" type circuit breaker is a circuit protection device which:• A) is free from the normal CB tripping characteristic • B) will allow the contacts to be held closed in order to clear a fault in the circuit • C) can be reset at any time • D) will not allow the contacts to be held closed while a current fault exists in the circuit

• 196) It may be determined that an aircraft is not properly bonded if:• A) there is heavy corrosion on the fuselage skin mountings. • B) a circuit breaker pops out. • C) there is interference on the VOR receiver. • D) static noises can be heard on the radio.

• 197) In which of the following circuits is a current limiter most likely to be fitted?• A) an EFIS display circuit • B) a low voltage DC circuit • C) a supply circuit • D) a lighting circuit

• 198) A carbon pile voltage regulator controls generator output using:• A) the secondary coil. • B) the armature feedback loop. • C) the field coil. • D) the reverse current relay.

• 199) A sine wave has a peak-to-peak voltage of 400 V. Its:• A) RMS value is 284 volts. • B) amplitude is 800 V. • C) RMS value is 141 V. • D) frequency is 50 Hz.

• 200) In a capacitive AC supply system, if frequency reduces:• A) current reduces. • B) inductive reactance increases. • C) capacitive reactance reduces. • D) current increases.

• 201) An auto-transformer:• A) has an primary winding which is isolated from the secondary winding. • B) converts AC to DC. • C) has a partially shared winding. • D) can be used for very large voltage step ups.