EASA : Module3 Electrical Fundamentals Question Part-1

EASA : Module3 Electrical fundamentals Question - Answer

What charge does the nucleus of an atom possess?

Ans a) Positive

b) Negative

c) Neutral

*

What is the maximum number of electrons in shell N of an atom?

a) 16

Ans b) 32

c) 18

*

Two 10V, 20 Ah batteries are connected in parallel and connected across a 10-ohm load. How long could they supply normal current before the voltage begins to decay?

a) 20 hours

b) 4 hours

Ans c) 40 hours

*

A 10 V battery supplies a resistive load of 10 ohms for 1 minute. What is the power supplied

a) 100 W

b) 10 VA

Ans c) 10 W

*

A 10V battery supplies a resistive load of 10 ohms for 1 minute. What is the work done?

a) 60J

b) 10J

Ans c) 600J

*

Three capacitors 10 microfarads, 10 nanofarads and 10 millifarads are connected in parallel. What is the total capacitance?

Ans a) 10.01001mF

b) 111mF

c) 1.001001mF

*

If a 1mF capacitor has a potential difference across it of 5V what is the energy stored?

a) 12.5 J

Ans b) 12.5 mJ

c) 25 mJ

*

A capacitor is fully charged after 25 seconds to a battery voltage of 20 V. The battery is replaced with a short circuit. What will be the voltage across the capacitor after 1 time constant?

a) 12.64 V

Ans b) 7.36 V

c) 0 V

*

Glass is an example of a

a) paramagnetic material

Ans b) diamagnetic material

c) coercive material

*

Which of the following is absolute permeability?

Ans a) µ

b) µo

c) µr

*

A solenoid of 10 turns per meter carries a current of 5A. If the current is reduced to 2.5A, how many turns would be required to maintain the same magnetic field?

a) 5

b) 50

Ans c

*

The point of coercivity occurs when the

a) magnetizing force applied causes the material to become magnetically saturated.

Ans b) magnetic flux is zero even though a magnetizing force is being applied.

c) magnetizing force reaches a peak positive or negative value.

*

What is the mutual inductance if two coils of 10mH and 500mH have 90% of the flux transferred from one to the other?

a) 4.5mH

b) 459mH

Ans c) 63mH

*

An inductor has 1,000 turns of wire and a cross sectional area of 0.001m2. If the core has a permeability of 0.000,001 and the coil is 0.1m what is the value of the inductor

Ans a) 10mH

b) 100microH

c) 100mH

*

Three inductors 10 mH, 5 mH and 20 mH are connected in parallel. What is the total inductance?

a) 35mH

Ans b) 2.86mH

c) Without knowing the coupling factor the total inductance cannot be found

*

If the current reaches a maximum through an inductor of 2A in 15 secs, what is the current after 3 secs?

Ans a) 1.26A

b) 0.63A

c) 1A

*

If the phase voltage in a star connected generator is 200V what will be the line voltage?

a) 115V

b) 200V

Ans c) 346V

*

A generator is labeled as having 115V/200V, 20A and PF 0.8. What is the apparent power in each line that the generator can produce?

a) 2.3kW

b) 2.3kVA

Ans c) 4kVA

*

A starter generator has a

a) low resistance series field and a low resistance shunt field

Ans b) low resistance series field and a high resistance shunt field

c) high resistance series field and a low resistance shunt field

*

Thermocouple harnesses are made from the same materials as the thermocouple so that

a) they will not corrode

Ans b) mini junctions are not formed

c) the resistance is not increased beyond limits

*

An oxygen molecule is made up of

Ans a) two oxygen atoms sharing electrons

b) two oxygen atoms sharing neutrons

c) two oxygen atoms sharing protons

*

A capacitor in a single phase AC motor is to

a) prevent spikes

b) block DC

Ans c) provide a phase shift

*

What value is the same as the equivalent D.C. heating effect?

Ans a) Root Mean Square

b) Average

c) Peak

*

What is the relationship between the voltage and the current in an A.C circuit containing resistance & inductance?

a) Current leads voltage by up to 90°

Ans b) Current lags voltage by up to 90°

c) Current lags voltage by 90°

*

What shape is the waveform when the input pulse and the time base are unequal?

a) Square

Ans b) Rectangular

c) Saw tooth

*

A sine wave has 5 amps RMS value. What is the peak value?

a) 6.37 amps

Ans b) 7.07 amps

c) 10 amps

*

In this circuit

Ans a) current leads voltage

b) current lags voltage

c) current = voltage

*

Decreasing the field current in a shunt motor will

a) increase speed and decrease torque

Ans b) increase speed and increase torque

c) decrease speed and increase torque

*

Power factor relates to

Ans a) true power and apparent power

b) KW and KVAR

c) horsepower and Watts

*

In a delta-connected generator

Ans a) line volts = phase volts, line current = root 3 times phase current.

b) line volts = phase volts, line current = phase current divided by root 3

c) line voltage = root 3 times phase voltage, line current = phase current

*

If current lags voltage by 90°, the circuit is

a) capacitive

b) resistive

Ans c) inductive

*

In a 3 phase motor, if 1 phase is lost, the motor

Ans a) remains at the same speed

b) runs at 1 third speed

c) runs at 2 thirds speed

*

A three-phase motor has the windings

Ans a) 120° apart

b) 90° apart

c) 180°apart

*

When measuring the phase and line voltages of a generator, it was found that line and phase voltages were equal. The generator is?

Ans a) delta wound

b) star wound.

c) either delta or star wound

*

To change the direction of a 3-phase induction motor you would

Ans a) swap two of the stator connections

b) swap all of the input connections

c) remove one of the input connections

*

To calculate generator output you need to know the

a) armature speed and number of series conductors

b) armature speed and number of parallel conductors

Ans c) armature speed and field strength

*

In a shunt motor, if you reverse both field current and armature current, the motor will

a) stop

b) change direction

Ans c) continue to run in the same direction

*

The permanent magnet in an A.C generator induces

Ans a) A.C. in the exitor generator

b) D.C. in the exitor generator

c) A.C. in the main generator

*

The slip speed of an induction motor is

Ans a) stator speed - rotor speed

b) stator speed + rotor speed

c) stator speed

rotor speed

*

The primary winding of a 3-phase transformer

a) is delta wound

b) is star wound

Ans c) could be either delta or star wound

*

The symbol for flux density is

a) H

Ans b) B

c) ø

*

A galvanometer measures

a) millivolts

b) megohms

Ans c) milliamps

*

A battery rated at 40 Ah will supply 200 mA for

Ans a) 200 hours

b) 5 hours

c) 20 hours

*

The unknown resistance R in the wheatstone bridge shown is

a) 1 ohm

Ans b) 4 ohms

c) 16 ohms

*

Which of the following materials is easiest to magnetize?

Ans a) Soft iron

b) High grade steel

c) Cast iron

*

AC generators are rated in

a) kVARs

b) kW

Ans c) kVA

*

To find which end of an electromagnet is the north pole, use the

a) Fleming's Left Hand Rule

Ans b) Right Hand Clasp Rule

c) Cork Screw Rule

*

A capacitor with double the area and double the dielectric thickness will have

a) double the capacitance

b) half the capacitance

Ans c) the same capacitance

*

In a transformer, if the rate of change of current increases, the mutual inductance will

a) increase

b) decrease

Ans c) remain the same

*

If the brake coil on an actuator motor goes open circuit, the actuator will

a) over-ride its mechanical stops

Ans b) stop

c) run slower

*

The frequency of the output of a 4 pole generator is 400 Hz. The generator is turning at

Ans a) 12000 RPM

b) 6000 RPM

c) 3000 RPM

*

What is the wave shape of the x-axis input of a traversing oscilloscope image?

a) square

b) rectangular

Ans c) triangular

*

An inductance/resistance motor is

a) better than a capacitance motor

b) restricted to low loads only

Ans c) less efficient than a capacitance motor

*

The voltage at point A is

Ans a) 7 V

b) 21 V

c) 28 V

*

A 4:1 step down transformer draws 115 V and 1 A. The output power will be

Ans a) 28.5 V at 4 A

b) 28.5 V at 16 A

c) 460 V at 0.25 A

*

The voltage induced in the stator of an AC generator is produced by

a) a fixed magnetic field

Ans b) a rotating magnetic field

c) an alternating field

*

A low frequency supply

Ans a) may damage inductive components

b) will have no effect on inductive components

c) will make the circuit operate faster due to the reduced impedance

*

A zinc-carbon battery life depends upon

a) the purity of the carbon rod

Ans b) the amount of zinc

c) the amount of the electrolyte paste

*

When checking the s.g. of the electrolyte in a lead acid battery, you should

Ans a) check all cells because they may be different

b) check only the no. 1 cell because it is the master cell

c) check any cell because they will all be the same

*

If electrons are added to an atom it becomes

a) a positive ion

Ans b) a negative ion

c) a neutral ion

*

An element whose atoms have fewer than 4 electrons in their valency shell are

Ans a) good conductors

b) good insulators

c) semiconductors

*

In a purely resistive AC circuit, the current vector is

Ans a) in phase with the voltage vector

b) +90^o out of phase with the voltage vector

c) -90^o out of phase with the voltage vector

*

The PD at the terminals of an open circuit battery with a small internal resistance will be

a) more than the EMF

b) less than the EMF

Ans c) the same as the EMF

*

The diagram shows a 200 V long shunt generator. What is the voltage dropped across the series resistor?

a) 200 V

Ans b) 0.12 V

c) 0.2 V

*

An electrolytic capacitor is used where

a) minimum losses are essential

Ans b) there is a polarized input

c) high frequency AC is used

*

If a connection to an AC motor is disconnected, the motor will

a) slow down and stop

Ans b) continue to run

c) stop

*

A band stop filter

Ans a) stops a narrow range of frequencies

b) stops frequencies either side of a narrow range

c) attenuates frequencies either side of a narrow range

*

This is a diagram of a

a) band pass filter

b) high pass filter

Ans c) low pass filter

*

When comparing the average values of an AC generator output, to the peak values

a) average voltage = same as the peak voltage

Ans b) average voltage = 0.63 x peak voltage

c) average voltage = 0.707 x peak voltage

*

A parallel circuit at resonance has

Ans a) maximum impedance

b) minimum impedance

c) zero impedance

*

A resistor dissipates 80 Watts. If it runs for 4 hours 15 minutes, how much energy is dissipated in total?

Ans a) 1.224 MJ

b) 20.4 kJ

c) 191.25 J

*

The earth lead of a 24 V equipment is 0.5 ohm resistance and carries 80 A. How much power does it dissipate?

Ans a) 3.2 kW

b) 1.152 kW

c) 1.92 kW

*

What must you do to make a 3 F capacitor circuit into a 2 F circuit?

a) Put a 1 F capacitor in series

b) Put a 2 F capacitor in parallel

Ans c) Put a 6 F capacitor in series

*

The time required to fully charge a 1 µF capacitor in series with a 100k ohm resistor is

Ans a) 100 ms

b) 1 s

c) 100 s

*

A capacitor is fully charged after 25 seconds to a battery voltage of 20 Volts. The battery is replaced with a short circuit. What will be the voltage across the capacitor after one time constant?

a) 12.64 volts

Ans b) 7.36 volts

c) 0 volts

*

The voltage rating of a capacitor is

Ans a) the max voltage that can be constantly applied

b) the min voltage required to charge

c) the normal operating voltage

*

The relative permittivity of a capacitor is

Ans a) the relative permittivity of the dielectric in relation to a vacuum

b) the permittivity of dielectric in relation to dry air

c) the permittivity of the dielectric

*

Magnetic inclination is the least at the

a) poles

Ans b) equator

c) isoclines

*

Ferromagnetic materials can be magnetized

a) within a band of temperatures

b) above a certain temperature

Ans c) below a certain temperature

*

Faradays Law States that

Ans a) the magnitude of the EMF is directly proportional to the rate of change of flux

b) the magnitude of the EMF is indirectly proportional to the rate of change of flux

c) the magnitude of the EMF is directly proportional to the magnetic flux

*

To reduce eddy currents in a transformer you would

Ans a) reduce the thickness of laminations in the magnetic core

b) increase the thickness of laminations in the magnetic core

c) reduce the number of turns on the primary winding

*

A transformer has an input of 400V and a ratio of 2:1. If the transformer is delta / star wound, what will the line voltage output be?

a) 115V

b) 200V

Ans c) 346V

*

What is the phase difference in a circuit with 100V, drawing 0.5 amps, consuming 50 Watts?

a) 45°

b) 90°

Ans c) 0°

*

In an A.C circuit, what happens if frequency is reduced?

a) Capacitive elements may be damaged

Ans b) Inductive elements may be damaged

c) There will be no effect

*

A Transformer with 115v primary voltage and a ratio of 5:1 is supplying a landing light (load 24v 45 amps) is used, what is the current drawn?

a) 205 amps

Ans b) 9 amps

c) 4.5 amps

*

A Transformer has 4500 secondary turns and 750 primary turns. Its turns ratio is

a) 1:6

Ans b) 6:1

c) 1/6

*

Two inductive coils are placed in close proximity with each other at 90 degrees. The number of flux linkages is

Ans a) 0

b) maximum positive

c) maximum negative

*

A high pass filter will?

Ans a) allow frequencies above a certain value to pass

b) allow frequencies below a certain value to pass

c) allow frequencies within a range to pass

*

If you apply this waveform to this circuit, what is the output across the capacitor?

a) Zero

b) Pulsed negative

Ans c) Pulsed positive

*

A 10 ohm resistor has a 14.14 V peak drop across it. What power is dissipated?

a) 19.99 W

Ans b) 10 W

c) 1.414 W

*

This is a symbol for

Ans a) a voltage dependant resistor

b) a variable differential resistor

c) a visual display rectifier

*

If a generator speed is halved and the field strength is doubled, the voltage output will be

a) halved

b) doubled

Ans c) unchanged

*

Point A on the armature of the generator shown is producing

Ans a) maximum current

b) minimum current

c) zero current

*

An accumulation of hydrogen on the plates of a battery is known as

a) hydration

Ans b) polarization

c) ionization

*

What is the power dissipated in a 500 ohm resistor with a 3A flow?

a) 1.5 kW

Ans b) 4.5 kW

c) 750 kW

*

Which of the following is 1 Amp?

Ans a) 1000 mA

b) 1000 μA

c) 1000 kA

*

A paramagnetic material has a relative permeability of

Ans a) greater than unity

b) less than unity

c) zero

*

What part of a battery is covered in hydrogen during polarization?

a) Cathode

Ans b) Anode

c) Both the anode and the cathode

*

Electricity conducts through

a) solids only

Ans b) solids and liquids

c) vacuum

*

The term that describes the combined resistive forces in an AC circuit is

Ans a) impedance

b) resistance

c) total resistance

*

How can the direction of rotation of a DC electric motor be changed

Ans a) reverse the electrical connections to either the field or armature windings

b) interchange the wires which connect the motor to the external power source

c) rotate the positive brush one commutator segment

*

An example of a good electrical insulator is

Ans a) glass

b) aluminium

c) mercury

*

The only practical method of maintaining a constant voltage output from an aircraft generator under varying conditions of speed and load is to vary the

Ans a) strength of the magnetic field

b) number of conductors in the armature

c) speed at which the armature rotates

*

An accumulation of hydrogen on the plates of a battery is known as

a) hydration

Ans b) polarization

c) ionization

*

Which of the following is most likely to cause thermal runaway in a nickel-cadmium battery

a) excessive current draw from the battery

Ans b) high current charging of the battery to more than 100 percent of its capacity

c) a high internal resistance condition

*

Electric motors are often classified according to the method of connecting the field coils and armature. Aircraft engine starter motors are generally of which type

a) compound

b) shunt (parallel)

Ans c) series

*

If a heavy mechanical load is removed from a series motor

a) the speed will decrease and the armature current will decrease

Ans b) the speed will increase and the armature current will decrease

c) the speed will increase and the armature current will increase

*

Static charges remaining in an aircraft are dissipated by

Ans a) the use of a conducting type nose wheel

b) bonding the aircraft to a refuel tanker

c) earthing the aircraft as soon as possible

*

Total resistance in parallel for R₁ and R₂ is

Ans a) R_T = (R₁ x R₂) ÷ (R₁ + R₂)

b) R_T = 1/R₁ + 1/R₂

c) 1/R_T = 1/R₁ + 1/R₂

*

The quill drive on an aircraft generator

a) makes possible the use of roller

b) damps out any commutator ripple

Ans c) damps out vibrations

*

The method of ascertaining the voltage of a standard aircraft lead-acid battery is by checking

a) the voltage on open circuit

b) the voltage with rated load switched ON

Ans c) the voltage off load

*

If the correct supply were connected to a DC shunt motor which had lost its residual magnetism it would

a) fail to run

b) run in the reverse direction

Ans c) run normally

*

A loss of electrical insulation results in

Ans a) a short circuit between the supply and earth

b) an open circuit between the supply and earth

c) an open circuit in the supply

*

A DC circuit containing a total resistance of 100 ohms has a current flow of 250 mA. The power dissipated in the circuit is

a) 0.4 watts

Ans b) 6.25 watts

c) 5 watts

*

Power is the rate of doing work. It is measured in

Ans a) joules/second

b) watts/second

c) joules x seconds

*

Ohm's law states that:

a) e.m.f. = current divided by resistance

b) resistance = current divided by e.m.f.

Ans c) current = e.m.f. divided by resistance

*

If the resistance of a resistor which is in series with two other resistors is doubled

a) the current in that resistance is doubled

b) the current in that resistance is halved

Ans c) the volts drop across that resistor increases

*

One purpose of a growler test is to determine the presence of:

Ans a) a shorted armature

b) an out-of-round commutator

c) a broken field lead

*

Through which material will magnetic lines of force pass the most readily?

a) aluminium

Ans b) iron

c) copper

*

Electricity conducts through

a) solids only

Ans b) solids and liquids

c) vacuum

*

The secondary coil of a transformer has 1500 turns and 10 Ω resistance. The primary coil has 1 k Ω resistance. How many turns does the primary coil have?

Ans a) 15,000

b) 150,000

c) 1,500,000

*

Two batteries 12V and 40 Ah each, are in series. What is the total capacity?

a) 12V 80 Ah

b) 24V 80Ah

Ans c) 24V 40 Ah

*

In a star wound primary transformer, how could you wind the secondary winding?

a) star only

b) delta only

Ans c) either delta or star

*

The phases in supply to a 2 phase motor are electrically

Ans a) 90 degrees apart from each other

b) 180 degrees apart from each other

c) 120 degrees apart from each other

*

A 30 KVA rated generator has a power factor of 0.8. What is its maximum consistent power

a) 30 KW

Ans b) 24 KW

c) 37.5 KW

*

A 50 μF capacitor is fed with a current of 25 mA. How long will it take to charge it to 100V?

a) 1 s

Ans b) 0.2 seconds

c) 12 minutes

*

The total resistance of the circuit shown is

a) 1.33 Ohms

b) 12 Ohms

Ans c) 3 Ohms

*

A step up transformer has

a) one winding

Ans b) two windings

c) three windings

*

The three voltages of a three phase generator are connected

Ans a) independently of each other

b) in series with each other

c) in parallel with each other

*

A photozoidal cell produces electricity when subjected to

Ans a) light

b) heat

c) pressure

*

 A thermocouple indicator is basically a type of

a) milliammeter

Ans b) millivoltmeter

c) milliohmeter

*

 An electric motor produces a force of 5 N at a distance of 0.2m from the centre of rotation and rotates at a speed of 100 revs/sec. The motors output is

a) 100 horsepower

Ans b) 628.4 watts

c) 314.2 watts

*

 A potentiometer varies

Ans a) voltage

b) current

c) resistance

*

Starter motors are usually

Ans a) series wound

b) compound wound

c) shunt wound

*

 How can it be determined if a transformer winding has some of its turns shorted together?

a) measure the input voltage with an ohmmeter

Ans b) the transformer will get hot in normal operation

c) the output voltage will be high

*

 An advantage of a star connected generator over a delta connected generator is

a) a balance load is guaranteed

Ans b) two potentials are available

c) the line and phase voltages are equal

*

 What does a rectifier do?

a) Changes direct current into alternating current

Ans b) Changes alternating current into direct current

c) Reduces voltage

*

 Two 12V 40 amp hour batteries connected in parallel will produce

a) 24V 80 ah

Ans b) 12V 80 ah

c) 24V 40 ah

*

 When an atom loses or gains an electron it is called

a) a current

Ans b) an ion

c) a molecule

*

 A circuit has a resistance of 50 ohms and an inductance of 0.2 Henry. If it is connected to a 200 volt 50 Hz supply the reactance will be

a) 31.42 ohms

Ans b) 62.84 ohms

c) 6.284 ohms

*

 A 24-volt source is required to furnish 48 watts to a parallel circuit consisting of four resistors of equal value. What is the voltage drop across each resistor?

a) 12 volts

Ans b) 24 volts

c) 3 volts

*

 Of the following which pair of materials would most readily become magnetized?

a) copper and steel

b) nickel and bronze

Ans c) iron and steel

*

 The formula for resistance in series is

Ans a) R_T = R₁ + R₂+ R₃...RN

b) R_T = R₁ x R₂x R₃...RN

c) 1/R_T = 1/ (R1 x R₂ x R₃...R_N)

*

The core material used for an electromagnet is soft iron because

Ans a) it demagnetizes easily

b) its magnetism is not easily destroyed

c) it retains most of its flux density when demagnetized

*

 What is the combined value of resistances of 4 ohm and 6 ohm connected in parallel?

a) 24 ohm

Ans b) 2.4 ohm

c) 0.24 ohm

*

Permanent magnets in an AC generator are

Ans a) to provide initial excitation

b) to control the frequency

c) to rectify the current

*

 The method of ascertaining the voltage of a standard aircraft lead-acid battery is by checking

Ans a) the voltage off load

b) the voltage on open circuit

c) the voltage with rated load switched ON.

*

 Generator brushes are normally made of

Ans a) carbon

b) brass

c) steel

*

 If the voltage across a resistor is doubled

Ans a) the current is doubled

b) the resistance is halved

c) the current is halved

*

 As the generator load is increases (within its rated capacity), the voltage will

a) remain constant and the amperage output will decrease

b) decrease and the amperage output will increase

Ans c) remain constant and the amperage output will increase

*

 If a number of resistors are connected in parallel, the total resistance is

a) the same as the lowest

Ans b) smaller than the lowest

c) greater than the lowest

*

 A charged body is said to have

Ans a) a surplus or deficiency of electrons

b) a surplus of protons

c) a deficiency of neutrons

*

 The ratio between apparent power and true power is the

a) efficiency

b) power rating

Ans c) power factor

*

 The voltage output of a generator is controlled by

a) varying the current of the output

b) varying the resistance of the output

Ans c) varying the current of the field

*

 The total current flowing in a circuit of 200 lamps in parallel, each of a resistance of 400 ohm and connected across an input of 100 volts is

Ans a) 50 amps

b) 25 amps

c) 40 amps

*

 The current flowing in the armature of a DC motor is equal to

a) (applied volts - generated volts) x armature resistance

b) applied volts + generated volts

armature resistance

Ans c) applied volts - generated volts

armature resistance

*

 In the circuit shown the 24 volt battery has an internal resistance of 1 ohm and the ammeter indicates a current of 12 amperes. The value of the load resistance is

Ans a) 1 ohm

b) 2 ohms

c) 6 ohms

*

 One advantage of using Ac electrical power in aircraft is

Ans a) the greater ease in stepping the voltage up or down

b) AC electrical motors can be reversed while dc motors cannot

c) the effective voltage is 1.41 times the maximum instantaneous voltage; therefore, less power input is required

*

 The quill drive on an aircraft generator

a) makes possible the use of roller bearings at the drive end

Ans b) damps out vibrations

c) damps out any commutator ripple

*

 The amount of electricity a capacitor can store is directly proportional to the

a) distance between the plates and inversely proportional to the plate area

b) plate area and is not affected by the distance between the plates

Ans c) plate area and inversely proportional to the distance between the plates

*

 When resistors are in parallel, the total resistance is

Ans a) smaller than the smallest resistor

b) the sum of all the resistors

c) larger than the smallest resistor

*

 What device is used to convert alternating current, which has been induced into the loops of the rotating armature of a DC generator into direct current as it leaves the generator?

Ans a) a commutator

b) an inverter

c) a rectifier

*

Two similar 12v batteries connected in parallel will produce

a) 24V e.m.f. with twice the capacity of each battery

b) 24v e.m.f. with the same capacity as each battery

Ans c) 12V e.m.f. with twice the capacity of each battery

*

 Unless otherwise specified, any values given for current or voltage in an AC circuit are assumed to be

a) maximum values

Ans b) effective values

c) instantaneous values

*

 If a heavy mechanical load is removed from a series motor

Ans a) the speed will increase and the armature current will decrease

b) the speed will decrease and the armature current will decrease

c) the speed will increase and the armature current will increase

*

 In a vector diagram showing the magnitude and direction of the inductance, capacitance and resistance in an AC circuit

Ans a) the inductive reactance would be in opposition to the capacitive reactance and resistance at 90 degrees

b) the inductive and capacitance reactance would be additive with the resistance subtractive

c) it is impossible to show values of this kind using vectors

*

 If service No. 1 is isolated from the supply busbar shown there will be

a) an increase in supply voltage

b) a decrease in supply voltage

Ans c) a decrease in total current consumption

*

 An increase in operating temperature in most electrical devices carrying current results in

Ans a) an increase in resistance and a decrease in current

b) a decrease in resistance and an increase in current

c) no effect on the resistance and current

*

E.M.F. in an electric circuit corresponds to what in a magnetic circuit

Ans a) mmf

b) flux

c) reluctance

*

Time constant of an inductor is

a) LR

Ans b) L/R

c) L²/R

*

Permanent magnets have

a) high reluctance, low coercive force

b) low reluctance, high coercive force

Ans c) high reluctance, high coercive force

*

A.C. value that can produce the same heat as D.C. is called

Ans a) r.m.s value

b) average value

c) peak value

*

If a battery has got low internal resistance, then

a) on load voltage will be greater than no load voltage

Ans b) no load voltage will be greater than on load voltage

c) no load voltage will be the same as on load voltage

*

In a parallel R, L, C circuit, the value of the capacitor is quadrupled, then the value of the impedance would

Ans a) reduce

b) increased

c) remain the same

*

In a circuit C = 25 microfarads and the current flow is 40 microamps for 4 seconds. What is the voltage

a) 12.8V

Ans b) 6.4V

c) 3.2V

*

A 3, 5 and 2 ohms resistance is connected in series with a 10 V battery. The voltage across the 2 ohms resistor is

a) 10V

Ans b) 2 V

c) 4 V

*

The power in a circuit when voltage and resistance is given can be found by

a) VxR

Ans b) VxV / R

c) VxVxR

*

A piezoelectric device generates electricity through

Ans a) pressure

b) friction

c) light

*

Conventional current flow inside a battery is from

Ans a) anode to cathode

b) cathode to anode

c) either anode to cathode or cathode to anode, depending on the active elements

*

Potentiometers are used as a

Ans a) variable voltage source

b) variable resistor

c) variable current source

*

In a transformer core loss is 200 W and copper loss is 220W at no load.

What is the core loss at full load

Ans a) 200 W

b) 220 W

c) 0 W

*

Calculate the speed of a 400 Hz, 4 pole machine

Ans a) 12,000 rpm

b) 6000 rpm

c) 8000 rpm

*

The purpose of end travel microswitch in a linear actuator is to

Ans a) remain closed and opens at end travel only

b) remain open and closes at end travel only

c) remain open during normal operation and only close if the actuator overruns its stops

*

Linear actuators used in aircraft are of

Ans a) split field series wound type.

b) split field shunt wound type

c) compound wound type

*

If a generator sparks, a possible reason is

Ans a) The brush springs are loose

b) The brushes have been placed around the magnetic coil

c) Magnetic flux deflecting the EMF

*

The charge on a proton is

a) neutral

Ans b) positive

c) negative

*

In conventional current flow, what is Fleming's right hand rule used for

a) Motors

Ans b) Generators

c) Inductors

*

In a capacitive circuit, if the frequency is increased

Ans a) the current increases

b) impedance increases

c) reactance remains the same

*

Three 12 µF capacitors are in series. The total capacitance is

a) 12 µF

Ans b) 4 µF

c) 36 µF

*

A 500 ohm resistor carries a 3 amp current. What is the power dissipated?

a) 5 kW

Ans b) 4.5 kW

c) 500 W

*

A paramagnetic material has a relative permeability

a) less than unity

Ans b) greater than unity

c) equal to unity

*

What is the PD of a circuit which has a 40 mA current and a 1 k ohm resistance?

a) 400 V

b) 4 V

Ans c) 40 V

*

The time constant of a capacitor is the time

Ans a) for the emf to reach 36.8% of maximum

b) the current to reach 70.7% of maximum

c) to reach maximum current

*

The secondary winding of a transformer has an impedance of 10 ohms and 1500 turns. For the primary winding to have an impedance of 1 k ohm, how many turns must it have?

a) 15,000

Ans b) 150,000

c) 1,500,000

*

A potentiometer has which of the following properties?

Ans a) 3 terminals

b) preset values

c) wire wound

*

A 3 ohm resistor dissipates 27 Watts. How much current flows through it?

Ans a) 3 A

b) 9 A

c) 0.15 A

*

In a 2 phase generator, how far apart are the windings electrically?

a) 45^o

Ans b) 90^o

c) 180^o

*

The SI unit of work is

a) Joules per second (Watts)

Ans b) Kilogram metres - force

c) Joules per metre

*

In the circuit below, what happens to the total circuit impedance if L is tripled?

Ans a) Increases

b) Remains the same

c) Reduces

*

In a voltaic cell, what is the build-up on the cathode called?

a) Polarization

Ans b) Sulphation

c) Hydration

*

A sine wave has a periodic time of 0.5 milliseconds. What is the frequency

a) 200 Hz

Ans b) 2 kHz

c) 20 kHz

*

Three branches in a circuit have currents entering of 3A, 4 A and 5 A. A forth branch has 10 A leaving. A fifth branch must have

a) 2A entering

Ans b) 2A leaving

c) 22A leaving

*

Where are the output windings on an AC generator?

Ans a) Stator

b) Rotor with slip rings

c) Rotor with commutator

*

If the field strength of a generator is doubled, and the speed is doubled, the output EMF will

Ans a) quadruple

b) double

c) stay the same

*

If the rate of change of current is halved, mutual inductance will

a) double

Ans b) stay the same

c) halve

*

If a capacitor of 50 microfarads has a current of 25 mA, how long does it take to charge to 100 V

Ans a) 200 milliseconds

b) 200 seconds

c) 150 seconds

*

In a Wheatstone Bridge, the ammeter reads zero, and the variable resistor is adjusted to 5 ohms. Resistor P has a value of 10 ohms and Q has a value of 100 ohms. What is the value of the unknown resistor?

Ans a) 0.5 ohms

b) 5 ohms

c) 50 ohms

*

In a tuned circuit at resonance, the circuit will be

a) inductive

Ans b) resistive

c) capacitive

*

The time constant for an inductor is

Ans a) L/R

b) R/L

c) L x R

*

In a DC motor the pole pairs are

Ans a) imbedded within the field coils

b) part of the armature

c) connected to the brush gear

*

Eddy currents in a transformer core are reduced by

Ans a) decreasing the thickness of the laminates

b) increasing the thickness of the laminates

c) making the core from a solid block

*

Transformer copper loss on full load is 220 Watts. On half load the loss will be

a) 110 Watts

b) 440 Watts

Ans c) 55 Watts

*

The earth's magnetic field is greatest at the

Ans a) magnetic poles

b) geographic poles

c) magnetic equator

*

If a 1 ohm circuit produces a 50 W output, the phase angle is

Ans a) 0^o

b) 90^o

c) 45^o

*

A series wound DC motor, the field has

Ans a) few turns of thick wire

b) few turns of thin wire

c) many turns of thin wire

*

What effect do the electrons of one atom have upon the electrons of another atom?

Ans a) They repel each other

b) They attract each other

c) They have no effect on each other

*

What is a molecule?

Ans a) The smallest part of a compound

b) The smallest part of an electron

c) The smallest part of an atom

*

A coulomb is

a) one ampere per second

Ans b) one ampere x second

c) one second per ampere

*

In a circuit containing three resistors of equal value connected in parallel, one resistor goes open circuit. The current in the other two resistors will

a) increase

b) decrease

Ans c) remain the same

*

20 amperes flow for 20 seconds. How many coulombs has flowed?

Ans a) 400

b) 20

c) 1

*

An atom is

Ans a) the smallest part of an element that retains its characteristics

b) the smallest part of a compound that can exist independently

c) the smallest particle of matter

*

A neutron is a particle which is

Ans a) contained within the nucleus of most atoms

b) orbits the nucleus of the atom

c) contained in the nucleus of all atoms

*

An electric current is a flow of

a) electrons from a positively charged area to a negatively charged area

b) protons from a positively charged area to a negatively charged area

Ans c) electrons from a negatively charged area to a positively charged area

*

An element could be considered to be a conductor if it has

a) a large number of electrons

b) a large number of electrons in its outer orbit

Ans c) a small number of electrons in its outer orbit

*

A volt can be considered to be a

Ans a) unit of electrical pressure

b) quantity of electrical energy

c) unit of electrical power

*

If the resistance of an electrical circuit is increased

a) the voltage will increase

b) the current will increase

Ans c) the current will decrease

*

If 2 coulombs flowed through a circuit in 2 seconds, the circuit would have

a) 2 volts PD

b) 2 amps

Ans c) 1 amp

*

In general, increasing the cross sectional area of an electrical cable

Ans a) enables it to carry more current

b) enables it to carry more voltage

c) increases its resistance

*

Doubling the running time of an electrical machine would

Ans a) double the joules used

b) double the watts used

c) double the current used

*

What is 3.25 volts in millivolts

a) 3.25 millivolts

Ans b) 3,250 millivolts

c) 325,000 millivolts

*

Electromotive force is measured in

a) Watts

b) Ohms

Ans c) Volts

*

Six resistors each of 6 ohms would be

a) 36 ohms in parallel

b) 1 ohm in series

Ans c) 1 ohm in parallel

*

A capacitor in a single phase motor is to

Ans a) provide a phase shift

b) prevent sparking at the switch

c) provide smoothing

*

The mass of an atom is contained mainly in the

a) electron

Ans b) nucleus

c) proton

*

The line voltage from a generator with a delta type connection will be

a) higher than the phase voltage

b) lower than the phase voltage

Ans c) the same as the phase voltage

*

On a linear actuator, the field cutoff coil will be energized when

Ans a) the actuator is running

b) the actuator is not running

c) only as the actuator commences movement

*

Kirchhoff's law states

Ans a) the algebraic sum of all the voltages entering or leaving a series of components will be equal to zero

b) the algebraic sum of all the currents entering or leaving a series of components will be equal to one

c) the inverse sum of all the voltages entering or leaving a series of components will be equal to one

*

The lines of magnetic flux from a magnet will

Ans a) repel each other

b) attract each other

c) have no effect upon each other

*

Two resistors are connected in series and have an e.m.f. of V volts across them. If the voltages across the resistances are V1 and V2 then by Kirchhoff's law

Ans a) V = V1 + V2

b) V2 = V1 + V

c) V1 = V2 + V

*

When an electrical supply becomes open-circuit

Ans a) the loss of continuity will prevent its component from functioning

b) the fuse or circuit breaker should isolate the circuit due to the increased current drawn

c) the component will operate normally but will not switch off

*

Some electric motors have two sets of field winding wound in opposite directions so that the

a) speed of the motor can be more closely controlled

Ans b) motor can be operated in either direction

c) power output of the motor can be more closely controlled

*

The amount of electrical power for a given generator weight is

a) determined by the size of the aircraft

b) greater for DC generator

Ans c) greater for AC generator

*

When resistors are in parallel the total current is equal to

a) the current through one resistor

Ans b) the sum of the currents

c) the reciprocal of all the currents

*

What is the ampere-hour rating of a storage battery that is designed to deliver 45 amperes for 2.5 hours?

a) 90.0 ampere-hour

Ans b) 112.5 ampere-hour

c) 45.0 ampere-hour

*

How much power must a 24-volt generator furnish to a system which contains the following series loads?

5 ohm, 3 ohm and 12 ohm

a) 450 watts

b) 402 watts

Ans c) 28.8 watts

*

A volt meter is connected

a) in series or parallel

Ans b) in parallel

c) in series

*

What polarity do interpoles take in a DC motor?

Ans a) The same as the next main pole behind in the direction of rotation

b) Either, provided they lay on the MNA

c) The same as the next main pole ahead in the direction of rotation

*

On a typical AC generator the output is taken

a) direct from the rotor via slip rings

b) direct from the exciter

Ans c) direct from the stator windings

*

Since electrical supplies taken from a bus-bar are in parallel, isolating some of the services would

Ans a) reduce the current consumption from the bus-bar

b) increase the current consumption from the bus-bar

c) not affect the current consumption, it would reduce the voltage

*

One Picofarad is

a) 1 x 1012 farad

b) 1 x 10-6 farad

Ans c) 1 x 10-12 farad

*

Which of these will cause the resistance of a conductor to decrease?

a) Decrease the length or the cross-sectional area

Ans b) Decrease the length or increase the cross-sectional area

c) Increase the length or decrease the cross-sectional area

*

The purpose of bonding is to

a) give generated static an easy return path to the generator

Ans b) stop different potentials developing with subsequent fire risks

c) ensure all components have been securely fitted

*

The S.I. unit of magnetic flux density is the

a) Weber

b) Henry

Ans c) Tesla

*

What is the principal advantage of the series-wound dc motor?

a) Low starting torque

b) Suitable for constant speed use

Ans c) High starting torque

*

Interpole windings fitted to DC series wound generators are

a) in series with the field

b) in parallel with the armature

Ans c) in series with the armature

*

One of the chief advantages of alternating current is that it can be transmitted at a high voltage with a low power loss; the voltage can then be changed to any desired value of

Ans a) AC by means of transformers

b) DC by means of transformers

c) DC by means of inverters

*

An AC generator is producing the required voltage but a higher frequency than that required. To remedy this, the following action must be taken?

a) Decrease the speed of the prime mover, and then decrease the strength of the field

b) Decrease the speed of the prime mover

Ans c) Decrease the speed of the prime mover, and then increase the strength of the field

*

How many amperes will a 28-volt generator be required to supply to a circuit containing five lamps in parallel, three of which have a resistance of 6 ohms each and two of which have a resistance of 5 ohms each?

Ans a) 25.23 amperes

b) 1 ampere

c) 1.11 amperes

*

The area of a hysteresis loop is proportional to the

Ans a) energy dissipated in putting the material through a complete cycle of magnetization and demagnetization

b) relative permeability of the material being magnetized

c) energy absorbed in completely demagnetizing the material

*

The current flowing through a circuit can be increased to four times its original value by

Ans a) doubling the applied voltage and halving the resistance

b) halving the applied voltage and halving the resistance

c) doubling the resistance and doubling the applied voltage

*

When more than two inductors of different inductances are connected in parallel in a circuit, the total inductance is

a) equal to the sum of the individual inductances

Ans b) less than the inductance of the lowest rated inductor

c) equal to the inductance of the highest rated inductor

*

What polarity do interpoles take in a DC generator?

Ans a) the same as the next main pole ahead in the direction of rotation

b) the same as the next main pole behind in the direction of rotation

c) either, providing they lay on M.N.A.

*

What happens to the resistance of a copper conductor when the temperature increases?

Ans a) It increases

b) It decreases

c) It remains the same

*

The method most often used in overcoming the effect of armature reaction is through the use of

a) shaded poles

Ans b) interpoles

c) drum-wound armatures in combination with a negatively connected series field

*

The core material used for an electromagnet is soft iron because

Ans a) it demagnetizes easily

b) it retains most of its flux density when demagnetized

c)its magnetism is not easily destroyed

*

The switch on a DC circuit containing a fully charged capacitor is opened. The voltage across the capacitor

a) drops immediately to zero

b) starts to fall exponentially to zero

Ans c) remains equal to the original charging voltage supply

*

in a 3 phase generator with balanced load, the potential between the neutral point and earth is

a) equal to line volts

b) equal to phase volts

Ans c) zero volts

*

A direct current of 12 milliamperes flows through a circuit which has a resistance of 1000 ohms. The power dissipated by the circuit is

a) 12 milliwatts

b) 12 watts

Ans c) 144 milliwatts

*

An increase in which of the following factors will cause an increase in the inductive reactance of a circuit?

a) Resistance and capacitive reactance

b) Resistance and voltage

Ans c) Inductance and frequency

*

in transformer operation, hysteresis losses are

a) current overcoming coil resistance

b) induced current in the iron core

Ans c) energy wasted in reversing core magnetization

*

The starting current of a series-wound DC motor, in passing through both the field and armature windings produces a

a) low starting torque

b) speed slightly higher when unloaded

Ans c) high starting torque

*

A non-magnetic metal

Ans a) has no permeability

b) has high retentivity

c) is a poor conductor

*

The power output of an AC parallel generator system is measured in

Ans a) KVA

b) KW / KVARS

c) amperes

*

The shape of the output waveform of an AC generator is known as a

Ans a) sine wave

b) cosine wave

c) frequency wave

*

in a circuit containing three resistors of equal value connected in series and one of the resistors short circuits, the effect is for the current in the other two resistors to

Ans a) increase

b) remain the same

c) decrease

*

To increase the speed of a shunt motor a resistance is placed

a) in series with the armature

b) in parallel with the field

Ans c) in series with the field

*

Frequency (Hz) is the number of cycles per

a) revolution

b) minute

Ans c) second

*

 In a series resistive circuit

a) the total voltage equals the difference between the individual voltages

Ans b) the total voltage is equal to the sum of the individual voltages

c) the total voltage is the same as the highest individual

*

The current in a DC circuit containing a fully charged capacitor is

Ans a) zero

b) is dependent upon the size of the capacitance of the capacitor

c) maximum

*

 The voltage of a secondary cell is

a) determined by the number of plates

b) determined by the area of the plates

Ans c) determined by the active materials on the plates

*

 The basis for transformer operation in the use of alternating current is mutual

a) reactance

Ans b) inductance

c) capacitance

*

 The exciter winding in a brushless AC generator is supplied with electrical power from

a) permanent magnets

Ans b) the busbar

c) a rotating generator integrally mounted on the same shaft as the AC windings

*

 If the cross-sectional area of a conductor is doubled, with voltage constant, the current will

a) halve

Ans b) double

c) remain constant

*

 Eddy currents in a transformer can be reduced by

a) using a special non metallic material

b) using a single solid piece of metal

Ans c) laminations

*

 If two resistors of 5 and 10 ohm respectively are connected in series and the current in the 5 ohm resistor is 1A. what is the current in the 10 ohm resistor?

a) 1/3 amp

b) it cannot be found without knowing the applied voltage

Ans c) 1 amp

*

 The term used to denote the strength of a magnetic field is

a) retentivity

b) hysterisis

Ans c) flux density

*

 At resonant frequency the phase difference between the voltage and current of an AC supply feeding an inductive and capacitive network is

Ans a) 0 degrees

b) 180 degrees

c) 90 degrees

*

 What is the ratio of turns between the primary coil winding and the secondary coil winding of a transformer designed to triple its input voltage?

a) primary will have three times as many turns as its secondary

b) primary will have twice as many turns as its secondary

Ans c) primary will have one-third as many turns as its secondary

*

 A direct current of 12 milliamperes flows through a circuit which has a resistance of 1000 ohms. The power dissipated by the circuit is

a) 12 milliwatts

b) 12 watts

Ans c) 144 milliwatts

*

 The voltage in a series circuit

Ans a) is different in each component

b) is the same in each component

c) is less than it would be in a parallel circuit

*

 Which aircraft circuit would be most likely to use frequency wild 200V AC?

Ans a) windscreen heating

b) hydraulic pump

c) standby compass

*

 Why are the iron cores of most induction coils laminated?

Ans a) To reduce the effects of eddy currents

b) To increase the core permeability

c) To reduce the core reluctance

*

 A 48-volt source is required to furnish 192 watts to a parallel circuit consisting of three resistors of equal value. What is the value of each resistor?

a) 12 ohm

b) 4 ohm

Ans c) 36 ohm

*

 If voltage is 100V, resistance is 25 ohms, what is the current?

a) 2500 amperes

Ans b) 4 amperes

c) 0.4 amperes

*

 A soft iron core is used in an ELECTRO magnet because

a) it has HIGH permeability and HIGH coercivity

Ans b) it has HIGH permeability and LOW coercivity

c) it has LOW permeability and HIGH coercivity

*

 The resistance to electrical flow in a wire depends on

Ans a) the diameter, length, material of wire and temperature

b) the material only - copper or aluminum

c) the length and material of the wire only

*

 A transformer should always have its

Ans a) secondary open circuit or on load

b) secondary shorted or on load

c) primary shorted or off load

*

 How can the direction of rotation of a DC electric motor be changed?

a) interchange the wires which connect the motor to the external power source

Ans b) reverse the electrical connections to either the field or armature windings

c) rotate the positive brush one commutator segment

*

 An AC generator's frequency will

a) always be constant regardless of the generators drive speed

b) vary with changes in field strength

Ans c) be proportional to the RPM at which it is driven

*

 A short circuit between the supply and earth

a) does not matter if the circuit uses the aircraft earth as a return

Ans b) could be very dangerous as the current drawn will be very high

c) is not dangerous as the current drawn will be low

*

 When two coils are linked by a common flux, a voltage can be induced in one by a changing current in the other. This process is known as

Ans a) mutual induction

b) the magnetic effect

c) self induction

*

 A circuit consists of 3 ohm, 5 ohm and 12 ohm resistors in series, the current flowing in the 5 ohm resistor is 10 amps. What is the applied voltage?

a) 100v

b) 10v

Ans c) 200v

*

Copper is an inferior conductor to aluminum when comparing

Ans a) weight for weight

b) load for load

c) CSA with CSA

*

In an AC circuit how is the value of true power calculated?

Ans a) By volts multiplied by amps multiplied by power factor

b) By wattmeter readings multiplied by power factor

c) By voltmeter readings multiplied by ammeter readings

*

 A frequency wild AC generator is used for

a) instruments and navigation

Ans b) de-icing loads

c) any AC load

*

 Which of the following is not one of the purposes of interpoles in a generator?

Ans a) Reduce field strength

b) Overcome armature reaction

c) Reduce arcing at the brushes

*

Which of the following would be used to calculate transformer turns ratio?

a) primary turns × secondary turns

b) primary turns ÷ secondary turns

Ans c) secondary turns ÷ primary turns

*

A good electrical insulator is a material which

a) has more protons than electrons

Ans b) has its electrons tightly bound to their parent atoms

c) contains a large number of positive ions

*

To reverse the direction of a series motor

a) the direction of the current through the field is reversed

Ans b) a second series field is fitted

c) the direction of the current through the field and the armature is reversed

*

How many cycles of AC voltage are produced in a six-pole alternator of the revolving-field type, with each revolution of the rotor?

a) Four

b) Six

Ans c) Three

*

The variable frequency output from an AC generator is used for

Ans a) supplying non-inductive loads

b) the AC supply instead of using inverters

c) driving AC operated instruments

*

The capacitance of a capacitor is dependant upon

Ans a) the type of material separating the plates

b) the rate of change of current in the circuit

c) the charge on it

*

A piece of equipment is rated at 750 watts and the applied voltage is 30 volts. The value of the protection fuse should be

a) 20 amps

Ans b) 30 amps

c) 15 amps

*

The current consumed by a DC starter motor will

a) remain relatively constant over the starting speed range

b) increase as the engine speed increases

Ans c) decrease as the engine speed increases

*

When different rated capacitors are connected in parallel in a circuit, the total capacitance is

a) equal to the capacitance of the highest rated capacitor

b) less than the capacitance of the lowest rated capacitor

Ans c) equal to the sum of all the capacitances

*

The voltage in a transformer secondary coil that contains twice as many loops as the primary coil will be

a) less and the amperage greater than in the primary coil

b) greater and the amperage greater than in the primary coil

Ans c) greater and the amperage less than in the primary coil

*

How are generators rated?

a) Impedance at rated voltage

b) Amperes at rated voltage

Ans c) Watts at rated voltage

*

in a single phase AC generator, frequency is determined by

Ans a) the generator speed

b) controlling the current flow through the voltage field windings

c) the number of pairs of poles

*

The risk of a fire due to static electricity is overcome

a) by fitting static wicks and insulating all metal components

Ans b) by connecting all metal components by bonding

c) by fitting static wicks and isolating the battery from inflammable gas sources

*

Due to armature reaction in a DC motor

Ans a) the trailing pole tips are magnetically weakened

b) the leading pole tips are magnetically weakened

c) the magnetic flux is restored by moving the MNA towards the GNA