b2 module 3 test 3

MODULE 03 PRACTICE MCQ

http://www.aircrafttechtrng.com

Which of the following converts light into electricity? Liquid crystal diode Light emitting diode Solar cell c

Which of the following are units of electrical power? Volts per ampere Joules per second Amperes per second b

Which law states that when a conductor is cut by magnetic lines of force an EMF is induced?

Lenz's Law Faraday's Law Kirchoff's Law b

When two inductors of 0.03 Henrys are connected in series, the total inductance is

0.03 H 0.015 H 0.06 H c

When two capacitors are connected in series the current flowing through each is directly proportional to its capacitance

the charge stored on each is the same

the charge stored on each is inversely proportional to the voltage across it

b

When the voltage applied to an inductor is disconnected, the collapsing field causes a back EMF which is

smaller than the applied voltage

equal to the applied voltage

bigger than the applied voltage c

When the nominal voltage of the aircraft electrical system is quoted as 24 volts, the generator supply is usually regulated to

28 volts 26 volts 24 volts

a

When removing a high voltage capacitor for testing it should

be fully charged be fully discharged retain a specified residual charge b

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

equal to the sum of the individual inductances

less than the inductance of the lowest rated inductor

equal to the inductance of the highest rated inductor

b

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

equal to the capacitance of the highest capacitor

less than the capacitance of the lowest capacitor

equal to the sum of all the capacitors c

When an electrical supply becomes open-circuit the loss of continuity will prevent its component from functioning

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

the component will operate normally but will not switch off a

When an electrical circuit is open circuited components will operate normally

resistance will be low resistance will be high b



When an atom loses or gains an electron it is called a current an ion a molecule b

When a current transformer is disconnected from a circuit it must be

left open circuit short circuited have a resistor connected across the terminals

b

When a conductor cuts the flux of a magnetic field an electromotive force (EMF) is induced in the conductor

there will be no effect on the conductor

the field will collapse

a

When a capacitor is charged from a DC supply the voltage / time curve is

logarithmic exponential linear b

What voltage does the neutral line carry in a star transformer?

combined line voltages zero voltage phase voltage b

What value of AC is the same as the equivalent DC heating effect?

root mean square average peak a

What units are used to measure potential difference between two points in an electrical circuit?

Coulombs Amps Volts c

What type of DC motor is used for starting engines? a series wound motor a shunt wound motor a compound wound motor a

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

cathode anode both the anode and the cathode b

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

put a 1 F capacitor in series

put a 2 F capacitor in parallel

put a 6 F capacitor in series c

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?

primary will have three times as many turns as its secondary

primary will have twice as many turns as its secondary

primary will have one-third as many turns as its secondary

c

What is the peak value of a sine wave with an amplitude of 10V RMS?

6.37V 14.14V 20V b

What is the frequency of a sine wave with a periodic time of 0.5 milliseconds?

200 Hz 20 kHz 2 kHz c

What is the effect of inserting an iron core into a current carrying coil?

The flux density of the original magnetic field produced by the coil is increased

The flux density of the original magnetic field remains constant

the core tends to move from a stronger to a weaker part of the field a



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

24 ohm 2.4 ohm 0.24 ohm b

What causes a transformer to be noisy? high coil resistance an air gap in the core high core losses b

Watt can be expressed as joules per second joules x seconds seconds per Joule a

Volts are units of electrical pressure

quantity of electrical energy

units of electrical power a

Voltmeters and ammeters usually indicate RMS values peak-to-peak values amplitudes a

Voltage regulation of an electrical generator in an aircraft is achieved by

control of the generators rotational speed

frequency control control of field current

c

Voltage is proportional to rate of change of current in inductors capacitors resistors a

Voltage is expressed in _______ and the basic SI units for it are _______ .

tension, C/J emf, J/C volts, J/C c

Voltage is a measure of the electrical charge passing a point in a circuit

power applied to an electrical circuit

potential difference between two or more points in a circuit

c

Voltage is a measure of potential differential coulombs per joule resistance to current a

Valence electrons are positively charged in the inner shell of an atom

in the outer shell of an atom c

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

V = V1 + V2 V2 = V1 + V V1 = V2 + V

a

Two resistors are colour coded (1) red, yellow, black, gold and (2) violet, blue, black, silver. They can both be replaced by a single resistor colour coded

brown, black, brown brown, black, black black, brown, black

a

Two objects at different levels of positive electrostatic charge will repel each other

be linked by a magnetic field

attract each other a

Two 470 microfarad capacitors, when connected in parallel, result in

235 microfarads 470 microfarads 940 microfarads a

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

24V, 80 ah 12V, 80 ah 24V, 40 ah b



To reverse the direction of rotation on a DC shunt motor, you must change the direction of the current through

the field windings or the armature windings

the armature windings only

the field windings and the armature windings a

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

in series with the armature

in parallel with the field in series with the field c

To convert from an RMS value to a peak value it is necessary to

multiply the RMS value by 0.707

multiply the RMS value

by 2

multiply the amplitude by 2 b

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

aluminum iron copper b

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

10.01001 mF 111 mF 1.001001 mF

a

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

12 F 4 F 36 F b

The windings of an autotransformer are on separate formers connected wired in parallel b

The windings of a three-phase motor are 120 apart 90 apart 180apart a

The voltage regulator of a DC generator ensures a reverse current flow when the electrical circuit is broken

maintains a constant voltage

increases voltage when engine RPM increases

b

The voltage rating of a capacitor is the max voltage that can be constantly applied

the min voltage required to charge

the normal operating voltage a

The voltage output of a shunt wound generator will rise gradually as load is applied

will remain constant as the electrical load increases

will fall gradually as load is applied c

The voltage output of a generator is controlled by varying the current of the output

varying the resistance of the output

varying the current of the field c



The voltage of an AC generator rises to max in one direction, falls to zero and rises in the same direction

rises to max in one direction then falls to zero then rises to max in the opposite direction

rises to max in one direction and remains

b

The voltage of a secondary cell is determined by the active materials on the plates

number of plates area of the plates a

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

a fixed magnetic field a rotating magnetic field

an alternating field b

The voltage induced in a conductor that is moving in parallel with magnetic lines of flux will be

zero proportional to the speed of movement

proportional to the flux density a

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

less and the amperage greater than in the primary coil

greater and the amperage greater than in the primary coil

greater and the amperage less than in the primary coil

c

The voltage across an inductor at a point in time is proportional to the

instantaneous current rate of change of current

value of capacitance b

The value of an AC sine wave that will give an equivalent heating effect in a DC resistor is the

average value RMS value peak value b

The unit of inductance is the Ohm Henry Reactance b

The type of windings commonly used in DC starter motors are

series wound shunt wound series shunt wound a

The true power in an AC circuit is given by voltmeter reading x PF volts x amps volts x amps x PF c

The total inductance of several inductors connected in series is

the sum of the individual inductances

the inverse of the sum of the individual inductances

the value of the highest inductance a

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

50 amps 25 amps 40 amps

a

The tolerance of a colour coded tubular ceramic capacitor is indicated by the

3rd band 4th band 5th band b

The Time Constant of an inductive circuit is LR LR LR b



The time constant of 5k resistor connected to a 2mH inductor is

400ns 10seconds 40ms a

The time constant in an inductive circuit is the time required for the current to reach

63.2% of maximum value

36.8% of maximum value

70.7% of maximum value a

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

impedance resistance total resistance a

The symbol for magnetic flux density is H B F b

The symbol for absolute permeability is o r a

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

drops immediately to zero

starts to fall exponentially to zero

remains equal to the original charging voltage supply

c

The sum of the instantaneous EMF's in a three phase system is

equal to the line voltage

three times the phase voltage

zero c

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

low starting torque speed slightly higher when unloaded

high starting torque

c

The SI unit of magnetic flux density is the Weber Henry Tesla c

The RMS value of an AC signal could be described as the average value for 1 complete cycle

half of the peak-to-peak value

the equivalent DC value c

The RMS value of a sine wave of 400V peak-to-peak is 200V 284V 141 V c

The RMS value of 200 volts peak to peak is 141.4 volts 70.7 volts 127.4 volts b

The resistance of a conductor is determined by its diameter, length, material and temperature

the material only - copper or aluminum

the length and material of the wire only a

The relative permittivity of a capacitor is the permittivity of the dielectric in relation to a vacuum

the permittivity of dielectric in relation to dry air

the permittivity of the dielectric a

The purpose of the commutator in an electrical generator is to change

DC to AC the direction of rotation AC to DC c

The property of a material to accept lines of flux is called

permeability reluctance retentivity a



The process that enables voltages to be induced between two coils that are not electrically connected is termed

mutual induction the transformer effect self induction

a

The primary winding of a 3-phase transformer is delta wound is star wound could be either delta or star wound c

The power output of a similar sized 3-phase compared to a single phase generator is

less same more c

The power in a DC circuit is equal to the voltage multiplied by the current

the current multiplied by the resistance

the voltage divided by the current a

The power factor of an AC circuit is the sine of the phase angle

cosine of the phase angle

tangent of the phase angle b

The Power Factor of a generator is sin cos tan b

The power dissipated by resistor is proportional to the voltage applied to it current flowing through it

square of the current flowing through it. c

The polarity of an electromagnet can be determined by using

Fleming's left hand rule

the right hand clasp rule

the corkscrew rule b

The point of coercivity occurs when the magnetizing force applied causes the material to become magnetically saturated

magnetic flux is zero even though a magnetizing force is being applied

magnetizing force reaches a peak positive or negative value b

The phase difference in a 2-phase motor is 90 degrees 180 degrees 120 degrees a

The permanent magnet in an AC generator induces AC in the excitor generator

DC in the excitor generator

AC in the main generator a

The period of a sine wave is the number of cycles per second

equal to the frequency the time required to complete one cycle c

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

more than the EMF less than the EMF the same as the EMF c

The output waveform of an AC generator is a sine wave cosine wave frequency wave a

The output of an AC generator is taken from the stator rotor, by slip rings rotor, by a commutator a



The output of a generator is controlled by varying the field strength

varying the speed of the engine

varying the length of wire in the armature windings

a

The output from a rotating armature AC generator would be taken from

the rotor the stator either the rotor or the stator a

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

strength of the magnetic field

number of conductors in the armature

speed at which the armature rotates a

The number of Watts in 2.5 kW is 2,500 Watts 25,000 Watts 250 Watts a

The mutual inductance of a transformer varies with the rate of change of current passing through the primary winding

the voltage induced in the secondary winding

the coefficient of coupling between the primary and secondary windings

c

The multiplier color coding on a capacitor is in farads microfarads picofarads c

The moving part of an AC generator is the stator the rotor the squirrel cage b

The most suitable type of capacitor to use in high voltage power supplies is

metalised film mica dielectric ceramic a

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

shaded poles interpoles drum-wound armatures in combination with a negatively connected series field

b

The maximum amount of flux that can be carried by ferro-magnetic material is termed

hysteresis saturation coercivity b

The main advantage of a starter-generator over conventional units is

for the same power output there is a weight reduction and the starter drive remains engaged

for the same power output there is a weight reduction and the drive is constantly engaged

it can produce a greater power output

b

The lines of magnetic flux from a magnet will repel each other attract each other have no effect upon each other a



The force that causes current to flow in an electrical circuit is termed

electrostatic force potential difference power b

The field windings of a shunt wound generator are in series with the commutator

in parallel with the armature

in series with the armature b

The electromagnetic force between two magnetised bodies is

proportional to the distance between them

inversely proportional to the distance between them

inversely proportional to the square of the distance between them c

The electrolyte in a NiCad battery is cadmium hydroxide nickel hydroxide potassium hydroxide c

The Earth's magnetic field is greatest at the magnetic poles geographic poles magnetic equator a

The discharge curve of a capacitor is linear logarithmic exponential c

The direction of rotation of a DC electric motor can be reversed by

interchanging the wires connecting the motor to the external power source

reversing the electrical connections to either the field or armature windings

rotating the 'positive' brush by one segment of the commutator b

The direction of a series motor cannot be reversed by

reversing the direction of the current through the field

supply current current through the armature b

The dielectric constant of a capacitor is a measure of its

capacity to store electrostatic energy

electrical resistance opposition to flow of electrons a

The current in a series tuned circuit at resonance is maximum minimum zero a

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

zero dependent upon the value of the capacitance

maximum

a

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

doubling the applied voltage and halving the resistance

halving the applied voltage and halving the resistance

doubling the resistance and doubling the applied voltage a

The current consumed by a DC starter motor will remain relatively constant over the starting speed range

increase as the engine speed increases

decrease as the engine speed increases c



The core material used for an electromagnet is soft iron because

it demagnetizes easily its magnetism is not easily destroyed

it retains most of its flux density when demagnetized

a

The copper loss on a single-phase transformer is 25 watts at full load. What will it be on half load?

5 watts 12.5 watts 6.25 watts c

The conductance of a material is inversely proportional to the current flowing through it

proportional to the applied voltage

inversely proportional to its resistance c

The commutator of a DC generator converts AC to DC AC to AC at a different voltage

DC to AC at a different voltage a

The common used symbol of resistance is V and it is measured in volts

R and it measured in ohms

P and it is measured in watts b

The combined resistance of several resistors connected in parallel is

less than the smallest resistor

greater than the largest resistor

equal to the average of the resistors a

The colour code of a 47k resistor is yellow, violet, orange orange, blue, red yellow, blue, orange a

The charge on the nucleus of an atom is positive negative neutral a

The charge on a proton is neutral positive negative b

The charge on a capacitor is expressed as the ratio Q/V the product Q x V the product C x V c

The charge on a capacitor is proportional to the current flowing through it

proportional to the voltage applied

inversely proportional to the voltage applied b

The capacity of a battery is expressed in watts volts ampere-hours c

The capacitance of a capacitor is dependant upon the type of material separating the plates

the rate of change of current in the circuit

the charge on it a

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

reactance inductance capacitance b

The back EMF in a DC motor is equal to the applied EMF

less than the applied EMF

greater than the applied EMF b

The aviation industry standard that has evolved for constant frequency aircraft is 115 / 200 V AC; 3-phase; 400 Hz. The 115 / 200 V are

peak-to-peak values RMS values amplitude values

b



The average value of 100 volts peak AC is 70.7 volts 141.4 volts 63.7 volts c

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

distance between the plates and inversely proportional to the plate area

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

plate area and inversely proportional to the distance between the plates

c

The amount of electrical charge transported by a current of 1amp in a time of 1 second is termed a

volt coulomb joule b

The ability of a resistor to dissipate power is determined mainly by its

temperature rating material and construction

cross sectional area b

Switching on or off the current in one coil produces an emf in another coil adjacent to it. The two coils are said to have

self inductance mutual inductance auto inductance

b

Starter motors are usually series wound compound wound shunt wound a

Split field motors enable alteration of torque direction of rotation speed b

Some electric motors have two sets of field windings wound in opposite directions. This enables

better control of the motor's speed.

the motor to be operated in either direction

better control of the motor's power output b

Solar cells generate electricity by converting heat from the sun sunlight chemical action b

Six resistors each of 6 Ohm would be 36 ohm in parallel 1 ohm in series 1 ohm in parallel c

RMS equals the peak amplitude multiplied by 2 divided by the square root of 2

multiplied by the square root of 3 b

Resistors of different value are connected in series with a supply. The voltage across each of them will be

different the same higher than it would be in a parallel circuit a

Resistors of 3, 5 and 12 are connected in series. If the current flowing through the 5 resistor is 10A, the applied voltage is

50V 20V 200 V

c

Reactive sparking is reduced by interpoles compensating windings

auxiliary windings a

Power is measured in joules/second watts/second joules x seconds a



Power in a DC circuit is found by multiplying current by resistance

multiplying the voltage by itself and dividing by the current

multiplying the resistance by the current squared

c

Power factor is defined as kVA / kW kVAR / kVA kW / kVA c

Potentiometers are used to provide variable voltages in a circuit

measure the voltage between two points in a circuit.

measure the current flowing in a circuit a

Potentiometers are constructed with 3 terminals preset values wire wound a

Phase angle is the difference in degrees of rotation between 2 alternating voltages or currents or a voltage and a current

the difference in degrees between the positive and negative parts of an AC sine wave

the cosine of the peak value of an AC voltage

a

Permeability of a material can be found by flux density / MMF MMF x flux density MMF / flux density a

Permanent magnets should be stored in pairs, end to end in a non-magnetic pox in pairs, with keeper plates c

Permanent magnets have high reluctance, low coercive force

low reluctance, high coercive force

high reluctance, high coercive force c

One pico Farad is 1 x 10Farad 1 x 10Farad 1 x 10Farad c

One Megohm equals 1,000 Ohms 10,000 Ohms 1,000,000 Ohms c

One advantage of using AC electrical power in an aircraft application is

the greater ease in stepping the voltage up or down

AC electrical motors can be reversed while dc motors cannot

less power input is required a

On which part of a DC motor would you find the poles? brushes stator rotor b

On a typical AC generator the output is taken direct from the rotor via slip rings

direct from the exciter direct from the stator windings c

On a brushless AC generator, the main rotating field winding is fed with

AC DC via diodes on the rotor

AC from the rotating field exciter b

Materials used for shielding sensitive electronic circuits from magnetic fields should have

high retentivity high permeabilty high reluctance b



Material with good electrical insulating properties has more protons than electrons

electrons tightly bound to their parent atoms

a large number of positive ions b

Magneto motive force m.m.f. can be found by N/I I x N Blv b

Lines of magnetic flux pass from N to S E to W S to N a

Kirchhoff's Law states that the algebraic sum of all the voltages entering or leaving a series circuit of components will be equal to zero

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

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

a

Interpole windings fitted to DC series-wound generators are

in series with the field in parallel with the load in series with the load c

Increasing the operating temperature of conductors carrying electrical current causes

an increase in resistance and a decrease in current

a decrease in resistance and an increase in current

no effect on the resistance and current a

Increasing the cross sectional area of an electrical cable

enables it to carry more current

enables it to carry more voltage

increases its resistance a

In transformer operation, hysteresis losses are current overcoming coil resistance

induced current in the iron core

energy wasted in reversing core magnetization

c

In their pure form, germanium and silicon are both insulators conductors semi-conductors a

In order to produce an alternating voltage of 400 Hz the number of pole-pairs required in an AC generator running at 6,000 rpm is

4

8

12 a

In conventional flow, the left hand rule applies to generators motors batteries b

In an LCR circuit, the ratio between apparent power and true power is termed the

efficiency factor efficiency rating power factor c

In an AC generator, the phase windings are usually mounted on the

stator rotor field electromagnet a



In an AC circuit, the effective voltage is equal to the maximum instantaneous voltage

greater than the maximum instantaneous voltage

less than the maximum instantaneous voltage c

In an AC circuit containing resistance and inductance, the

current leads voltage current lags voltage current and voltage are

in phase b

In AC generators 0.637 of the peak voltage is the RMS average value form factor b

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

star only delta only either delta or star c

In a single-phase AC generator, frequency is determined by

the generator speed controlling the current flow through the voltage field windings

the number of pairs of poles a

In a simple voltaic cell, polarization reduces output voltage because of the

transfer of material between the anode and the cathode

build up of hydrogen on the anode

build up of hydrogen on the cathode b

In a shunt wound DC generator, the field winding and armature winding are connected in

parallel differential compound series a

In a shunt motor, if both field and armature currents are reversed, the motor will

stop change direction continue to run in the same direction c

In a series wound DC motor, the field has few turns of thick wire few turns of thin wire many turns of thin wire a

In a series tuned circuit, at frequencies above resonance, the

current and voltage are in phase

voltage leads the current

current leads the voltage b

In a series tuned circuit at resonance the current leads the voltage

the voltage leads the current

the current and voltage are in phase c

In a series resistive circuit, the total voltage is equal to the difference between the individual voltages

the sum of the individual voltages

the highest individual voltage b

In a series LCR circuit at resonance, R = 100 ohm, L and C are each 10 ohm. The total impedance is

100 ohms 120 ohms zero a

In a resistive circuit, doubling the EMF will double the resistance halve the current double the current c

In a purely resistive AC circuit, the current vector is in-phase with the voltage vector

+90 out of phase with the voltage vector

-90 out of phase with the voltage vector a

In a purely resistive AC circuit, increasing the frequency will

increase the resistance decrease the resistance

not affect the resistance c



In a parallel tuned circuit, at frequencies below resonance, the

voltage and current are in phase



In a parallel RLC circuit, the value of the capacitor is quadrupled, then the value of the impedance would

reduce increased remain the same a

In a parallel LCR circuit, if the capacitance is increased by 4 times, what happens to the impedance?

increases by 4 times decreases by 75% remains the same c

In a delta-connected generator line current = phase current multiplied by root 3

line current = phase current divided by root 3

line current = phase current a

In a Delta wound system the line current is equal to phase current root 3 x phase current less than the phase current b

In a DC shunt motor, if the field resistance increases, the back EMF

increases decreases remains the same b

In a DC motor, the back EMF increases if the motor speed increases speed falls load rises a

In a DC circuit, power = 100 watts and voltage = 50 volts. What is the resistance?

2 Ohm 25 Ohm 50 Ohm b

In a circuit containing resistors in parallel, the voltage is the same in all parts of the circuit

the sum of the voltage drops equals applied voltage

resistance is determined by value of current flow a

In a balanced Wheatstone bridge, the current through the centre of the bridge is

zero maximum positive maximum negative a

In a 3-phase motor, if 1 phase is lost, the motor remains at the same speed

runs at 1 third speed runs at 2 thirds speed a

In a 3-phase generator, what angle are the phases to each other?

180 120 90 b

In a 3 phase delta connected AC generator line voltage is greater than phase voltage

line current is equal to phase current

line voltage is equal to phase voltage c

In a 2-phase generator, what angles are the phases to each other?

90 180 360 a

Impedance is the combined effect of resistance and reactance

real and imaginary power

resistance and conductivity a



If the voltage in a resistive circuit is doubled, the current is

halved inverted doubled c

If the voltage across a resistor is doubled the current is doubled the resistance is halved

the current is halved a

If the temperature of a pure metal is reduced to absolute zero, its resistance will be

infinity practically zero unaffected b

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

halved doubled unchanged c

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

double stay the same halve b

If the phase voltage in a star connected generator is 115V what is he line voltage?

115 V 200 V 346 V b

If the phase and line voltages from a 3-phase generator are equal, the generator is

delta connected star connected unbalanced a

If the output frequency of a 4 pole generator is 400 Hz, it's speed is

12,000 RPM 6,000 RPM 3,000 RPM a

If the North Pole of a magnet is brought nearer to the North Pole of another magnet

attraction between them will be increased

repulsion between them will be increased

repulsion between them will be reduced b

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

quadruple double stay the same a

If the field current to a shunt wound DC motor is decreased when operating at a constant load, the motor speed will

reduce increase not change

b

If the diameter of a conductor is doubled, its current carrying capacity will

half double multiply by 12.6 c

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

1.26 A 0.63 A 1 A a

If the cross-sectional area of a conductor is increased, its resistance will

remain the same decrease increase b

If the cross sectional area of a conductor is doubled, the maximum voltage it can carry will

half double remain the same c



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

fail to run run in the reverse direction

run normally c

If the area and thickness of a capacitor's dielectric are both doubled, its capacitance will

double half remain the same c

If electrons are added to an atom it becomes a positive ion a negative ion a neutral ion b

If an insulated conductor is placed near to a negatively charged rod, the nearest end of the conductor becomes

negatively charged positively charged no change will occur b

If an AC sinewave has an RMS value of 5V its peak value is

14.14 V 6.37 V 7.07 V c

If a voltage of 10 V is applied to a resistance of 250 ohms, what current will flow?

25 amps 4 milliamps 40 milliamps c

If a transformer winding has some of its turns shorted together

the input voltage will reduce

the transformer will get hot in normal operation

the output voltage will be high b

If a heavy mechanical load is removed from a series motor

the speed will decrease and the armature current will decrease

the speed will increase and the armature current will decrease

the speed will increase and the armature current will increase b

If a generator sparks, a possible reason is the brush springs are loose

the brushes have been placed around the magnetic coil

magnetic flux deflecting the EMF a

If a DC circuit with a total resistance of 2 Ohms has 12 volts DC applied the resulting current would be

24 A 0.167 A 6 A c

If a current is passed through a conductor that is positioned in a magnetic field

the current will increase

a force will be exerted on the conductor

there will be no effect unless the conductor is moved

b

If a constant current of 25 ma is flowing through a capacitor of 50 microfarads, how long will it take to charge to 100 V?

200 milliseconds 200 seconds 150 seconds

a

If a battery had no internal resistance, its no-load voltage would be

lower than its on-load voltage

higher than its on-load voltage

the same as its on-load voltage c



If a bar magnet is cut in half the magnet is destroyed

two bar magnets are formed

one bar magnet and one non-magnet is formed b

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

2 volts 2 amps 1 amp c

Hydrogen atoms consist of two protons and one electron

two neutrons and two protons

one proton and one electron c

How much power is supplied by a 24V generator connected to two 12 ohm resistors in parallel?

144 watts 576 watts 96 watts c

How much power is dissipated when a current of 3A flows through a 500 ohm resistor?

1.5 kW 4.5 kW 15 W b

How many millivolts are there in 7.25 volts? 0.725 7,250 725,000 b

How many amperes are there in 10,000 micro amps? 10 A 0.01 A 0.1 A b

How are generators rated? impedance at rated voltage

amperes at rated voltage

watts at rated voltage c

Generators are usually excited by a permanent magnet

externally excited self excited c

Generator brushes are normally made from carbon brass steel a

Frequency (Hz) is the number of cycles per revolution minute second c

Electrons from different atoms have no effect on each other

attract each other repel each other c

Electromotive force is measured in watts ohms volts c

Electrolytic capacitors have a large physical size for a large capacity

small physical size for a large capacity

small physical size for low leakage current b

Electrolytic capacitors are used for low loss applications polarised inputs high frequency AC b

Electricity conducts through solids only solids and liquids vacuum b

Electrical power is expressed in Watts Coulombs Volts a



Electrical charges build up on aircraft in flight due to friction the conductive skin of the aircraft cutting the Earth's magnetic flux

chemical action between the aircraft skin and the moisture in the air a

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

compound

shunt

series

c

Electric lines of force between two negatively-charged objects will

cross over each other attract each other repel each other c

Eddy currents in a transformer can be reduced by constructing the core with

special non-metallic material

a single, solid piece of soft iron

laminated formers c

Doubling the running time of an electrical machine would double the

joules used watts used current used a

Devices that generate electricity by immersing dissimilar metals in an electrolyte are

photo-voltaic cells voltaic cells thermo-electric cells b

Decreasing the field current in a shunt motor will increase speed and decrease torque

increase speed and increase torque

decrease speed and increase torque b

DC generator circuits incorporate reverse current relays to

protect the battery against excessively high back EMFs

allow the charge rate to drop as the battery becomes charged

prevent the battery from motoring the generator c

Copper losses in a transformer are caused by circulating currents through the transformer

the resistance in the windings

wasting of the copper wires due to friction b

Conventional current inside a discharging battery flows from

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

b

Connecting batteries in series increases the capacity; voltage remains the same

increases the voltage and capacity

increases the voltage; the capacity remains the same

c



Connecting batteries in parallel increases the capacity; the voltage remains the same

increases the voltage and capacity

increases the voltage; the capacity remains the same

a

Commutator ripple can be reduced by using a ripple filter increasing the speed of rotation

connecting a resistor in series with the armature a

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

remain constant and the amperage output will decrease

decrease and the amperage output will increase

remain constant and the amperage output will increase

c

As a lead-acid cell discharges, its internal resistance decreases increases remains constant b

Armature reaction is reactive sparking due to dirty or worn commutator

the MMF opposing rotation c

Applying friction to an insulating material alters the number of electrons in its atoms

has no effect on its atomic structure

alters the number of protons in its atoms a

Apparent Power is measured in KW or Watts KVA or VA KVAR or VAR b

Apparent power in an AC circuit is found by V x I V x I x cos V x I x sin a

An oxygen molecule contains two oxygen atoms with shared

electrons neutrons protons a

An LCR circuit supplied with 100 V draws 0.5 amps, and consumes 50 watts. The phase difference between the votage and current is

180 90 0

c

An induced current in a coil opposes the EMF producing it

aids the EMF producing it

does not affect the EMF producing it a

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

resistance and capacitive reactance

resistance and voltage inductance and frequency c

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

a good conductor a good insulator a semiconductor a

An electrical circuit contains 3 resistors of equal value connected in parallel. The total current in the circuit will be equal to

the current flowing through one resistor

three times the current in one resistor

one third the current in one resistor b



An electric current is a flow of electrons from a positively charged area to a negatively charged area

protons from a positively charged area to a negatively charged area

electrons from a negatively charged area to a positively charged area

c

An electric current is an excess of free electrons

an excitement of electrons in a metal

an ordered flow of electrons c

An atom is the smallest part of an element that retains its characteristics

the smallest part of a compound that can exist independently

the smallest particle of matter a

An alternator delivers 500V RMS at 1 ampere with at a power factor is 08. What is the true power?

100 VA 400 W 500 W b

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

a balanced load is guaranteed

two voltages are available

the line and phase voltages are equal b

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

hydration polarization ionization b

An AC generator has an output of 200 KVA. The real load is 140 KW. The power factor is

1.43 0.3 0.7 c

An AC circuit has a power factor of 0.8, and is drawing 10 A at 100 Volts. How many watts are being used?

1250 watts 1000 watts 800 watts c

According to Ohm's Law, the current in a DC circuit is proportional to both the voltage and the resistance

inversely proportional to the resistance and proportional to the voltage

inversely proportional to the voltage regardless of the resistance b

According to Lenz's Law, the polarity of the current induced in a coil

is the same as the polarity of the voltage producing it

increases the strength of the magnetic field producing it

opposes the magnetic field producing it b

According to Faraday's Law, an EMF induced in a coil has the same polarity as the current producing it

has a magnitude proportional to the rate of change of flux

opposes the magnetic field producing it b

AC value that can produce the same heat as DC is called

rms value average value peak value a

AC frequencies are expressed in degrees/second cycles per minute Hertz c



A wire is rotated through a magnetic field. To produce a DC output it must be connected to

a commutator slip rings a rectifier a

A two-phase induction motor has 2 poles 3 poles 4 poles c

A tuned circuit at resonance is inductive resistive capacitive b

A transformer with a 5:1 ratio has a 24 V output. What is the input?

120 VDC 4.8 VAC 120 VAC c

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

205 amps 9 amps 4.5 amps

b

A transformer rated at a frequency of 200 Hz may be used at any other frequency

may only be used at the rated frequency or above

may only be used at the rated frequency or below

b

A transformer is designed to operate at 80 Hz. It is connected across a 60 Hz supply. The primary windings would

draw more current draw less current draw the same current

a

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?

115 V 200 V 346 V

c

A transformer has 500 turns on the primary and 100 turns on the secondary. When connected to a 100 V supply, the output is

500 V 20 V 25 V

b

A transformer has 1200 turns primary and 4800 turns secondary. What value of load resistance would be required to give a reflected impedance of 1000 Ohm

1 kohm 4 kohm 16 kohm

c

A step up transformer has one winding two windings three windings b

A starter generator has a low resistance series field and a low resistance shunt field

low resistance series field and a high resistance shunt field

high resistance series field and a low resistance shunt field

b

A soft iron core is used in an electro-magnet because it has

high permeability and high coercivity

high permeability and low coercivity

low permeability and high coercivity b



A single-phase circuit has an input voltage of 100 V. The current is 10 A and the circuit has a power factor of 0.5. The true power is

1000 W 50 W 500 W

c

A sine wave of RMS value 7.07 volts has a peak to peak value of

10 volts 0.707 volts 20 volts c

A sine wave has a frequency of 20 Hz. Its period is 0.05 seconds 20 cycles per minute 5 milliseconds a

A shunt motor gives constant torque with variations in speed

rotates at constant speed

produces a high starting torque b

A series motor draws a high current on start, and then the current reduces. This is due to

the resistance of the field and the armature in series

the back EMF the resistance of the field and armature in parallel

b

A pure capacitor, inductor and resistor are connected in series and the voltage drops across each are 10 V. The total current flowing in the circuit is 1 A. How much true power is the circuit consuming?

30 VA 30 W 10 W

c

A piezo-electric device generates electricity through pressure friction light a

A photovoltaic cell produces electricity when subjected to

light heat pressure a

A permanent magnet suspended in the Earth's atmosphere will

rotate at the same speed as the Earth

align itself with the Earth's magnetic field

always point towards the geographic North Pole b

A parallel circuit with any number of 2 terminal connections

has the same current throughout

the individual voltage drops is equal to the emf

the resistance is dependent on current b

A non-magnetic metal has no permeability has high retentivity is a poor conductor a

A neutron is a particle which is contained within the nucleus of most atoms

orbiting around the nucleus of the atom

contained in the nucleus of all atoms a

A molecule is the smallest part of a compound an electron an atom a



A material's opposition to flow of current is termed its resistance reluctance conductance a

A material with a narrow hysteresis loop has high retentivity has low retentivity cannot be magnetised b

A high surge of current is required when a DC electric motor is first started. As the speed of the motor increase

the applied emf increases proportionally

the counter emf decreases proportionally

the counter emf builds up and opposes the applied emf, thus reducing the current flow through the armature

c

A high pass filter has high impedance to low frequency, low impedance to high frequency

high impedance to high frequency, low impedance to low frequency

high impedance to both high and low frequency

a

A high pass filter attenuates frequencies above a certain value below a certain value within a particular band b

A good conductor has a large number of electrons

a large number of electrons in its outer orbit

a small number of electrons in its outer orbit

c

A generator supplies 25 A, 4 V and 50 W. What is the apparent power and the power factor?

100 VA and 2 400 VA and 0.5 100 VA and 0.5 c

A generator rated at 30 KVA and power factor 08 has a maximum continuous power output of

30 kW 24 kW 37.5 kW b

A generator is taken off-line by creating a short circuit operating the field switch

removing all loads b

A fully charged battery rated at 24 V, 60 Ah, is connected to a 48 watt light bulb. Approximately how long will the battery last?

30 hrs 120 hrs 2.5 hrs

a

A filter with a small bandwidth has a high value of Q a low value of Q a Q of zero a

A filter comprising a capacitor in series and inductor in parallel with the load is a

band pass filter high pass filter low pass filter b



A DC shunt motor has 28 volts applied. The current taken from the armature of 2 Ohm resistance is 1 amp. The Back EMF is

30 V 27 V 26 V

c

A Coulomb is a current flow of one ampere per second

one ampere x second one second per ampere b

A conventional aircraft AC generator will be series wound delta wound star wound c

A component consuming 80 watts at 8 amps would require a supply of

10 Volts 100 Volts 5 Volts a

A circuit comprises a 5ohm resistor connected in series with a 10 ohm resistor. If the current in the 5 ohm resistor is 1 A, what is the current in the 10 ohm resistor?

2 amps It cannot be found without knowing the applied voltage.

1 amp

c

A charged body is said to have a surplus or lack of electrons

a surplus of protons a lack of neutrons a

A capacitor is used in a single phase AC motor to prevent spikes block DC provide a phase shift c

A capacitor is a barrier to both AC and DC AC DC c

A capacitor connected to a 20V battery is fully charged after 25 seconds. If the battery is replaced with a short circuit, what will be the voltage across the capacitor after 1 time constant?

12.64 V 7.36 V 1 V

b

A battery voltage "V" is connected to R1 and R2 that are in parallel. If R1 has 2 amps running through it and is twice the value (resistance) of R2 then the total current flowing from the battery is

3 amps 4 amps 6 amps

c

A battery rated at 40 Ah will supply 200 mA for 200 hours 5 hours

20 hours a

A band stop filter passes all frequencies above a specified value

attenuates frequencies either side of a narrow range

passes frequencies either side of a narrow range

c

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

5 kW 4.5 kW 500 W b



A 400 Hz, 4-pole motor will rotate at 12,000 rpm 6,000 rpm 8,000 rpm a

A 3-phase star-delta wound transformer gives 90 phase shift no phase shift 30 phase shift c

A 3-phase induction motor can be reversed by isolating one phase reversing the rotor connections

changing over any two phases

c

A 3-phase AC generator has 3 separate stator windings spaced at

90 60 120 c

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

30 KW 24 KW 375 KW b

A 20 pico Farad capacitor with a 1MW resistor takes how long to charge?

20 milli seconds 0.1 millisecond 10 seconds b

A 2 Ohm resistor has 3 amps through it. What power is being consumed by the resistor?

18 joules per second 18 watts 6 watts b

A 2 Ohm resistor has 3 amps flowing through it. What is the voltage across the resistor?

0.67 volts 1.5 volts 6 volts c

A 1F capacitor is equivalent to 0.000,001 Farads 1,000,000 Farads 0.001 Farads a

1 ampere equals 1,000,000 milliamps 100 milliamps 1,000 milliamps

c

The direction of current induced in a wire rotating in a magnetic field can be determined by

Fleming's right hand rule

Fleming's left hand rule

cork screw rule a

A 3 phase system, with one end of each phase connected to a common neutral point, is known as

a star connection a line connection a delta connection a

In a parallel tuned circuit, at frequencies below resonance, the

voltage and current are in phase



In a parallel RLC circuit, the value of the capacitor is quadrupled, then the value of the impedance would

reduce increased remain the same a

In a parallel LCR circuit, if the capacitance is increased by 4 times, what happens to the impedance?

increases by 4 times decreases by 75% remains the same c

In a delta-connected generator line current = phase current multiplied by root 3

line current = phase current divided by root 3

line current = phase current a



In a Delta wound system the line current is equal to phase current root 3 x phase current less than the phase current b

In a DC shunt motor, if the field resistance increases, the back EMF

increases decreases remains the same b

In a DC motor, the back EMF increases if the motor speed increases speed falls load rises a

In a DC circuit, power = 100 watts and voltage = 50 volts. What is the resistance?

2 Ohm 25 Ohm 50 Ohm b

In a circuit containing resistors in parallel, the voltage is the same in all parts of the circuit

the sum of the voltage drops equals applied voltage

resistance is determined by value of current flow a

In a balanced Wheatstone bridge, the current through the centre of the bridge is

zero maximum positive maximum negative a

In a 3-phase motor, if 1 phase is lost, the motor remains at the same speed

runs at 1 third speed runs at 2 thirds speed a

In a 3-phase generator, what angle are the phases to each other?

180 120 90 b

In a 3 phase delta connected AC generator line voltage is greater than phase voltage

line current is equal to phase current

line voltage is equal to phase voltage c

In a 2-phase generator, what angles are the phases to each other?

90 180 360 a

Impedance is the combined effect of resistance and reactance

real and imaginary power

resistance and conductivity a

If the voltage in a resistive circuit is doubled, the current is

halved inverted doubled c

If the voltage across a resistor is doubled the current is doubled the resistance is halved

the current is halved a

If the temperature of a pure metal is reduced to absolute zero, its resistance will be

infinity practically zero unaffected b

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

halved doubled unchanged c

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

double stay the same halve b



If the phase voltage in a star connected generator is 115V what is he line voltage?

115 V 200 V 346 V b

If the phase and line voltages from a 3-phase generator are equal, the generator is

delta connected star connected unbalanced a

If the output frequency of a 4 pole generator is 400 Hz, it's speed is

12,000 RPM 6,000 RPM 3,000 RPM a

If the North Pole of a magnet is brought nearer to the North Pole of another magnet

attraction between them will be increased

repulsion between them will be increased

repulsion between them will be reduced b

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

quadruple double stay the same a

If the field current to a shunt wound DC motor is decreased when operating at a constant load, the motor speed will

reduce increase not change b

If the diameter of a conductor is doubled, its current carrying capacity will

half double multiply by 12.6 c

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

1.26 A 0.63 A 1 A a

If the cross-sectional area of a conductor is increased, its resistance will

remain the same decrease increase b

If the cross sectional area of a conductor is doubled, the maximum voltage it can carry will

half double remain the same c

Which rule is used to determine the direction of the magnetic field surrounding a conductor?

Right hand screw rule Fleming's left hand rule

Fleming's right hand rule a

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

decrease its cross-sectional area

increase its cross-sectional area

increase its length b

Which of the following types of resistor dissipates power most effectively?

Carbon film. Metal oxide Ceramic wire-wound c

Which of the following types of capacitor is most stable?

Mica dielectric Electrolytic Ceramic dielectric a

Which of the following materials is easiest to magnetize?

soft iron high grade steel cast iron a

Which of the following is used to calculate transformer turns ratio?

primary turns secondary turns

primary turns/ secondary turns

secondary turns/ primary turns b



Which of the following is the best insulator? silicon gold ceramic c

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

reduce field strength overcome armature reaction

reduce arcing at the brushes a

Which of the following is 1 Amp? 1000 mA 1000 A 1000 kA a

Which of the following formulae is used to calculate the total resistance of resistors connected in parallel?

1/R = 1/(R1 + R2) R = R1 + R2 1/R = 1/R1 + 1/R2 c

The line voltage in a Star-wound transformer is root 3 / phase voltage the same as phase voltage

root 3 x phase voltage c

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

higher than the phase voltage

lower than the phase voltage

the same as the phase voltage c

The life of a zinc-carbon battery depends upon the purity of the carbon rod

the amount of zinc the amount of the electrolyte paste b

The iron cores of induction coils are laminated to reduce the effects of eddy currents

increase the core permeability

reduce the core reluctance a

The inductance of several coils connected in parallel is the sum of the individual inductances

the inverse of the sum of the inverses of the individual inductances

the sum of the individual inductances divided by the number of inductors

b

The impedance of an ac circuit is measured in kilovolt-amperes ampere ohm c

The impedance of a parallel LCR circuit at resonance is

maximum minimum zero a

The hysteresis loop for a magnetic material is a graph of

total flux against flux density

current against flux density

flux density against magnetizing force c

The ground lead of a 24 V equipment has a resistance of 0.5 Ohm and carries 80 A. How much power does it dissipate?

3.2 kW 1.152 kW 1.92 kW a

The frequency of a power wave in an AC resistance circuit is

the same as the frequency for voltage and current

half the frequency for voltage and current

twice the frequency for voltage and current c

b2 module 3 test 3

Documents

Transcript of b2 module 3 test 3