An inductor is said to be saturated when.

it will no longer accept lines of flux

the current through it is zero.

In a DC motor, the stator's magnetic field, due to armature reaction, moves.

in the opposite direction of rotation of the armature.

in the same direction of rotation of the armature.

A small air gap between magnetic poles results.

in the same field as a large air gap, for the same magnetising force.

in a weaker field than a large air gap, for the same magnetising force.

in a stronger field than a large air gap, for the same magnetising force.

The electromagnetic brake coil in an actuator would be energised.

only when the actuator is running.

only at the instant of starting and stopping.

In a shunt wound direct current motor with a constant voltage field supply, the torque developed by the motor is.

directly proportional to armature current.

inversely proportional to the armature current

Decreasing the field current in a shunt motor will.

increase speed and increase torque.

decrease speed and increase torque.

increase speed and decrease torque.

To calculate generator output you need to know the.

armature speed and field strength.

armature speed and number of series conductors.

armature speed and number of parallel conductors

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

continue to run in the same direction

A starter generator has a.

low resistance series field and a high resistance shunt field.

low resistance series field and a low resistance shunt field.

high resistance series field and a low resistance shunt field

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

reverse the electrical connections to either the field or armature windings.

rotate the positive brush one commutator segment.

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

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.

speed at which the armature rotates.

number of conductors in the armature.

If a heavy mechanical load is removed from a series motor.

the speed will increase and the armature current will decrease.

the speed will increase and the armature current will increase.

the speed will decrease and the armature current will decrease

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

remain closed and opens at end travel only.

remain open and closes at end travel only.

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

If a generator sparks, a possible reason is.

magnetic flux deflecting the EMF.

the brushes have been placed around the magnetic coil.

In a DC motor the pole pairs are.

embedded within the field coils

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

only as the actuator commences movement.

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

remain constant and the amperage output will increase.

remain constant and the amperage output will decrease.

decrease and the amperage output will increase.

The voltage output of a generator is controlled by.

varying the current of the field.

varying the current of the output.

varying the resistance of the output.

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

(applied volts-generated volts) / armature resistance.

(applied volts-generated volts) * armature resistance.

applied volts + generated volts / armature resistance

To reverse the direction of a series motor.

a second series field is fitted

the direction of the current through the field and the armature is reversed.

the direction of the current through the field is reversed.

The current consumed by a DC starter motor will.

fecrease as the engine speed increases.

remain relatively constant over the starting speed range.

increase as the engine speed increases

Due to armature reaction in a DC motor.

the trailing pole tips are magnetically weakened.

the leading pole tips are magnetically weakened.

the magnetic flux is restored by moving the MNA towards the GNA.

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

motor can be operated in either direction.

speed of the motor can be more closely controlled.

power output of the motor can be more closely controlled

What polarity do interpoles take in a DC motor?.

The same as the next main pole behind in the direction of rotation.

Either, provided they lay on the MNA.

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

What is the principal advantage of the series-wound DC motor?.

Suitable for constant speed use.

What polarity do interpoles take in a DC generator?.

the same as the next main pole behind in the direction of rotation.

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

the same as the next main pole ahead in the direction of rotation.

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

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

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

speed slightly higher when unloaded.

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

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

the counter emf decreases proportionally.

the applied emf increases proportionally.

Quiz

Física 3

oriol arrufat 200 questions

Take the quiz

Questions in this quiz (200)

11 Volt is produced when a current of 1 Amp per second is varied in a coil'. This is a definition of.
1. A1 Ampere per metre.
2. B1 Henry.
3. C1 Coulomb per second.
2Two inductor coils in very close proximity; if one of the coils is rotated 90 degrees slowly away from the other the mutual inductance.
1. Adecreases.
2. Bremains the same.
3. Cincreases
3An inductor is said to be saturated when.
1. Athe current is at a maximum.
2. Bthe current through it is zero.
3. Cit will no longer accept lines of flux
4In a DC motor, the stator's magnetic field, due to armature reaction, moves.
1. Ain the same direction of rotation of the armature.
2. Bin the opposite direction of rotation of the armature.
3. Cinto alignment with the GNA.
5A small air gap between magnetic poles results.
1. Ain a weaker field than a large air gap, for the same magnetising force.
2. Bin a stronger field than a large air gap, for the same magnetising force.
3. Cin the same field as a large air gap, for the same magnetising force.
6The electromagnetic brake coil in an actuator would be energised.
1. Aonly at the instant of starting and stopping.
2. Ball the time in flight.
3. Conly when the actuator is running.
7In a shunt wound direct current motor with a constant voltage field supply, the torque developed by the motor is.
1. Aindependent of load.
2. Bdirectly proportional to armature current.
3. Cinversely proportional to the armature current
8Decreasing the field current in a shunt motor will.
1. Adecrease speed and increase torque.
2. Bincrease speed and increase torque.
3. Cincrease speed and decrease torque.
9To calculate generator output you need to know the.
1. Aarmature speed and number of series conductors.
2. Barmature speed and field strength.
3. Carmature speed and number of parallel conductors
10In a shunt motor, if you reverse both field current and the armature current, the motor will.
1. Astop.
2. Bchange direction.
3. Ccontinue to run in the same direction

11A starter generator has a.
1. Alow resistance series field and a low resistance shunt field.
2. Blow resistance series field and a high resistance shunt field.
3. Chigh resistance series field and a low resistance shunt field
12If the brake coil on an actuator motor goes open circuit, the actuator will.
1. Arun slower.
2. Bstop.
3. Cover-ride its mechanical stops
13The diagram shows a 200 V long shunt generator. What is the voltage dropped across the series resistor?.
1. A0.12 V.
2. B0.2 V.
3. C200 V.
14If a generator speed is halved and the field strength is doubled, the voltage output will be.
1. Aunchanged.
2. Bdoubled.
3. Chalved.
15How can the direction of rotation of a DC electric motor be changed?.
1. Areverse the electrical connections to either the field or armature windings.
2. Brotate the positive brush one commutator segment.
3. Cinterchange the wires which connect the motor to the external power source
16The only practical method of maintaining a constant voltage output from an aircraft generator under varying conditions of speed and load is to vary the.
1. Aspeed at which the armature rotates.
2. Bstrength of the magnetic field.
3. Cnumber of conductors in the armature.
17Electric motors are often classified according to the method of connecting the field coils and armature. Aircraft engine starter motors are generally of which type?.
1. ACompound.
2. BShunt (parallel).
3. CSeries
18If a heavy mechanical load is removed from a series motor.
1. Athe speed will increase and the armature current will increase.
2. Bthe speed will increase and the armature current will decrease.
3. Cthe speed will decrease and the armature current will decrease
19 If the correct supply were connected to a DC shunt motor which had lost its residual magnetism it would.
1. Arun in the reverse direction.
2. Bfail to run.
3. Crun normally.
20One purpose of a growler test is to determine the presence of:.
1. Aa shorted armature.
2. Ba broken field lead.
3. Can out-of-round commutator.
21 The purpose of an end-travel microswitch in a linear actuator is to.
1. Aremain open and closes at end travel only.
2. Bremain open during normal operation and only close if the actuator overruns its stops.
3. Cremain closed and opens at end travel only.
22Linear actuators used in aircraft are of.
1. Asplit field series wound type.
2. Bcompound wound type.
3. Csplit field shunt wound type
23If a generator sparks, a possible reason is.
1. Athe brush springs are loose
2. Bmagnetic flux deflecting the EMF.
3. Cthe brushes have been placed around the magnetic coil.
24 If the field strength of a generator is doubled, and the speed is doubled, the output EMF will.
1. Astay the same.
2. Bdouble.
3. Cquadruple.
25In a DC motor the pole pairs are.
1. Aconnected to the brush gear.
2. Bpart of the armature.
3. Cembedded within the field coils
26A series wound DC motor, the field has.
1. Afew turns of thin wire.
2. Bmany turns of thin wire.
3. Cfew turns of thick wire
27Doubling the running time of an electrical machine would.
1. Adouble the current used.
2. Bdouble the joules used.
3. Cdouble the watts used
28On a linear actuator, the field cutoff coil will be energized when.
1. Aonly as the actuator commences movement.
2. Bthe actuator is not running.
3. Cthe actuator is running.
29An 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.
1. A100 horsepower.
2. B628.4 watts.
3. C314.2 watts.
30Starter motors are usually.
1. Aseries wound.
2. Bcompound wound.
3. Cshunt wound
31Generator brushes are normally made of.
1. Asteel.
2. Bcarbon.
3. Cbrass.
32As the generator load is increased (within its rated capacity), the voltage will.
1. Aremain constant and the amperage output will decrease.
2. Bdecrease and the amperage output will increase.
3. Cremain constant and the amperage output will increase.
33The voltage output of a generator is controlled by.
1. Avarying the current of the output.
2. Bvarying the resistance of the output.
3. Cvarying the current of the field.
34The current flowing in the armature of a DC motor is equal to.
1. A(applied volts-generated volts) / armature resistance.
2. B(applied volts-generated volts) * armature resistance.
3. Capplied volts + generated volts / armature resistance
35What 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?.
1. AAn inverter.
2. BA commutator.
3. CA rectifier
36Which of the following is not one of the purposes of interpoles in a generator?.
1. AOvercome armature reaction.
2. BReduce arcing at the brushes.
3. CReduce field strength
37To reverse the direction of a series motor.
1. Athe direction of the current through the field and the armature is reversed.
2. Bthe direction of the current through the field is reversed.
3. Ca second series field is fitted
38The current consumed by a DC starter motor will.
1. Aremain relatively constant over the starting speed range.
2. Bfecrease as the engine speed increases.
3. Cincrease as the engine speed increases
39How are generators rated?.
1. AImpedance at rated voltage.
2. BAmperes at rated voltage.
3. CWatts at rated voltage.
40Due to armature reaction in a DC motor.
1. Athe leading pole tips are magnetically weakened.
2. Bthe trailing pole tips are magnetically weakened.
3. Cthe magnetic flux is restored by moving the MNA towards the GNA.
41Some electric motors have two sets of field winding wound in opposite directions so that the.
1. Aspeed of the motor can be more closely controlled.
2. Bmotor can be operated in either direction.
3. Cpower output of the motor can be more closely controlled
42What polarity do interpoles take in a DC motor?.
1. AEither, provided they lay on the MNA.
2. BThe same as the next main pole ahead in the direction of rotation.
3. CThe same as the next main pole behind in the direction of rotation.
43What is the principal advantage of the series-wound DC motor?.
1. ASuitable for constant speed use.
2. BHigh starting torque.
3. CLow starting torque.
44Interpole windings fitted to DC series wound generators are.
1. Ain series with the armature.
2. Bin series with the field.
3. Cin parallel with the armature.
45What polarity do interpoles take in a DC generator?.
1. Athe same as the next main pole behind in the direction of rotation.
2. Beither, providing they lay on M.N.A.
3. Cthe same as the next main pole ahead in the direction of rotation.
46The method most often used in overcoming the effect of armature reaction is through the use of.
1. Ashaded poles.
2. Binterpoles.
3. Cdrum-wound armatures in combination with a negatively connected series field
47The starting current of a series-wound DC motor, in passing through both the field and armature windings produces a.
1. Aspeed slightly higher when unloaded.
2. Bhigh starting torque.
3. Clow starting torque.
48To increase the speed of a shunt motor a resistance is placed.
1. Ain parallel with the field.
2. Bin series with the field.
3. Cin series with the armature.
49A 200 volt motor is taking 10 amperes armature current, the armature resistance is 0.1 ohm. The Back-EMF under these conditions will be.
1. A201 volts.
2. B199 volts.
3. C1 volt.
50What is a method used for restoring generator field residual magnetism?.
1. AEnergize the armature.
2. BFlash the fields.
3. CReseat the brushes.
51A high surge of current is required when a DC electric motor is first started. As the speed of the motor increase.
1. Athe counter emf decreases proportionally.
2. Bthe applied emf increases proportionally.
3. Cthe counter emf builds up and opposes the applied emf, thus reducing the current flow through the armature
52Aircraft generators are cooled by.
1. Afuel cooling radiators.
2. Boil cooling radiators around the main body.
3. Cram air.
53On a combined DC starter - generator system.
1. Athe voltage regulator is connected to the shunt field after the start cycle is completed.
2. Bthe voltage regulator controls the start sequence during engine starting.
3. Cthe series coil is open circuit during the engine start sequence
54 If the field current to a shunt wound DC motor is decreased when operating at a constant load, the motor speed will.
1. Areduce.
2. Bnot change.
3. Cincrease.
55If a motor is spinning at 50 cycles per second, how long is 1 cycle of the output?.
1. A50 seconds.
2. B0.83 seconds.
3. C0.02 seconds
56 In a an DC motor, the rotation of the MNA.
1. Ais opposite to the rotation of the armature.
2. Bis slightly less speed than the rotation of the armature.
3. Cis the same as the rotation of the armature
57In a wave wound generator with 4 poles, what would be the minimum number of brushes?.
1. A4.
2. B2.
3. C8.
58 A wire is rotated through a magnetic field. To give DC it must be connected to.
1. Aa commutator.
2. Bslip rings.
3. Ca rectifier.
59If the supply to a DC shunt motor was reversed.
1. Ait would rotate in the same direction.
2. Bit would fail to run.
3. Cit would rotate in the opposite direction
60A series motor draws a high current on start, and then the current reduces. This is due to.
1. Athe resistance of the field and the armature in series.
2. Bthe resistance of the field and armature in parallel.
3. Cthe back EMF.
61Interpoles in a DC generator are connected.
1. Ain series with the armature.
2. Bin series with the field.
3. Cin parallel with the armature
62In a DC generator, the effect of armature reaction may be reduced by moving the brush gear.
1. Ain the direction of armature rotation towards the MNA.
2. Bfrom MNA to GNA.
3. Cagainst the direction of armature rotation towards the MNA
63The windings embedded in the pole faces of a DC generator are.
1. Acommutating coils.
2. Binterpoles.
3. Ccompensating windings
64A 6 pole wave-wound generator has.
1. A3 brushes.
2. B2 brushes.
3. C6 brushes.
65Armature reaction in a DC generator causes.
1. AMNA to move in the opposite direction of rotation.
2. BMNA to move in the direction of rotation.
3. CGNA to move in the direction of rotation.
66 In a DC motor, back-EMF rises if the motor.
1. Aspeed falls.
2. Bspeed faload rises.
3. Cspeed rises.
67A DC generator armature has 6 poles and is lap wound. The number of brushes required are.
1. A2
2. B3
3. C6
68Reactive sparking is reduced by.
1. Ainterpoles.
2. Bcompensating windings.
3. Cauxiliary windings
69The back-EMF in a DC motor is.
1. Aequal to the applied EMF.
2. Bless than the applied EMF.
3. Cgreater than the applied EMF.
70The flux density of a magnetic field is 1.5T. The length of the conductor in the field is 2 m and the current flowing through the conductor is 5 amps. The force on the conductor is.
1. A0.6 Newtons.
2. B15 Newtons.
3. C3.75 Newtons
71 A DC shunt motor has 28 volts applied. The current taken from the armature of 2 ohms resistance is 1 amp. The Back-EMF is.
1. A26 V.
2. B30 V.
3. C27 V.
72In a motor, armature reaction causes the MNA to move.
1. Aagainst the direction of rotation.
2. Bin the direction of rotation.
3. Cto the GNA
73The diagram shown is a.
1. Ashunt wound machine.
2. Bshort shunt compound wound machine.
3. Clong shunt compound wound machine.
74In a generator system, a stabilizing winding is used.
1. Ain series with the field to prevent oscillations.
2. Bto control output current.
3. Cto prevent voltage overshoot.
75What part of a DC motor would you find the poles?.
1. Abrushes.
2. Brotor.
3. Cstator
76The main advantage of a starter-generator over conventional units is.
1. Ait can produce a greater power output.
2. Bfor the same power output there is a weight reduction and the starter drive remains engaged.
3. Cfor the same power output there is a weight reduction and the drive is constantly engaged.
77An A.C. shunt wound motor sometimes uses a volts dropping resistor. The resistor would be.
1. Ain series with the field.
2. Bin series with the supply.
3. Cin series with the armature.
78Commutator ripple can be reduced by.
1. Aincreasing generator frequency.
2. Bthe use of a ripple filter.
3. Ca resistor in series with the armature.
79 In a DC motor the interpoles are part of the.
1. Arotor assembly.
2. Bstator assembly.
3. Cfield
80Armature reaction is.
1. Athe MMF opposing rotation.
2. Bdue to dirty or worn commutator.
3. Creactive sparking
81A shunt motor.
1. Ais constant speed.
2. Bhas high starting torque.
3. Cgives constant torque with variations in speed.
82In a DC shunt motor, if the field resistance is increased what happens to the back EMF?.
1. Adecreases.
2. Bremains the same.
3. Cincreases
83To increase the voltage output of a generator you can.
1. Adecrease speed.
2. BIt is not speed dependant.
3. Cincrease speed.
84Generator voltage is.
1. Adependant on speed of rotation.
2. Bindependent of speed of rotation.
3. Cnot dependant on speed of rotation
85The output from a generator to a commutator is.
1. Apulsed DC.
2. BDC.
3. CAC
86What is the main disadvantage of a starter generator?.
1. AHeavier than like for like.
2. BWill not supply output at low rpm.
3. CCan only be used on piston engines
87Back-EMF is the greatest when a motor is.
1. Aat operating speed.
2. Bunder heavy load.
3. Cjust starting to rotate
88When a conductor carrying a current and placed in a magnetic field it experiences.
1. Aan electrostatic force.
2. Ban electromagnetic force.
3. Ca magnetic force.
89The type of motor used in a linear actuator is.
1. Aparallel (shunt wound).
2. Bcompound.
3. Cseries.
90If the speed of a coil in a magnetic field is doubled and the field strength is doubled the output will.
1. Aquadruple.
2. Bstay the same.
3. Chalve
91How many brushes are used in an 8 pole wave wound machine.
1. A6
2. B8
3. C2
92In the shunt generator the field is supplied by.
1. Athe load.
2. Bthe armature.
3. Ca separate supply.
93Increasing the speed of an aircraft generator results in an automatic.
1. Afield circuit resistance decrease.
2. Barmature circuit resistance increase.
3. Cfield circuit resistance increase
94 Which generators are usually used on aircraft?.
1. AShunt.
2. BCompound.
3. CSeries
95In a cumulative compound wound generator the.
1. Athe series and shunt fields assist each other.
2. Bthe series and shunt fields oppose each other.
3. Cthe voltage falls suddenly with an increase in load
96The shunt wound generator is controlled by a variable resistance in.
1. Aparallel with the field.
2. Bseries with the armature.
3. Cseries with the field.
97The series wound generator's terminal voltage will, when below saturation.
1. Aincrease with an increase in load.
2. Bdecrease with an increase in load.
3. Cdecrease with a decrease in rotational speed
98The shunt wound generator is normally started.
1. Aon load.
2. BEither of the above.
3. Coff load
99How do you reduce ripple on the output of a DC generator?.
1. AIncrease the speed of the armature and add more turns.
2. BDecrease the speed of the armature and add more series windings.
3. CIncrease the commutator segments and connect each to a separate parallel winding
100Armature reaction in a DC motor causes the neutral axis to shift in.
1. Athe direction in the direction of armature rotation.
2. Bthe direction opposite to the direction of armature rotation.
3. Ceither direction depending on current flow.
101An indication of good commutation on a DC machine would be.
1. Ahigh armature currents.
2. Blittle or no sparking at the commutator.
3. Csilent operation of the machine.
102If compound DC generators are operated in parallel they must.
1. Aall rotate at the same speed.
2. Bhave an equalising or load sharing loop.
3. Call use the same voltage
103The windings embedded in the pole faces of a generator are.
1. Acommutating coils.
2. Binterpoles.
3. Ccompensating coils
104Prolonged reactive sparking in a DC generator could damage the.
1. Aarmature.
2. Bcommutator.
3. Cpole pieces.
105The poles of a DC generator are laminated to.
1. Areduce eddy current losses.
2. Breduce flux losses.
3. Creduce hysteresis losses
106One advantage of a DC motor over an AC motor is.
1. Athe direction of rotation of the rotor can be changed.
2. Bless voltage is required in DC than AC.
3. Cthe DC motor will use less current
107In a shunt wound direct current motor the torque is.
1. Ainversely proportional to the current in the armature.
2. Bindependent of load.
3. Cproportional to the current in the armature
108Convention requires that in a symmetrical 3 phase system, the.
1. Ared voltage is taken as the reference phase.
2. Byellow voltage phase leads the red phase by 120 degrees.
3. Cred voltage phase leads the blue phase by 120 degrees.
109What is the phase difference in a circuit with 100V, drawing 0.5 amps, consuming 50 Watts?.
1. A0°.
2. B45°.
3. C90°.
110The power factor of a circuit containing an imbalance of inductive and capacitive reactance is.
1. Agreater than unity.
2. Bunity.
3. Cless than unity.
111If you apply this waveform to this circuit, what is the output across the capacitor?.
1. APulsed negative.
2. BPulsed positive.
3. CZero.
112What value is the same as the equivalent D.C. heating effect?.
1. APeak.
2. BAverage.
3. CRoot Mean Square.
113What shape is the waveform when the input pulse and the time base are unequal?.
1. ASaw tooth.
2. BSquare.
3. CRectangular.
114A sine wave has 5 amps RMS value. What is the peak value?.
1. A7.07 amps.
2. B6.37 amps.
3. C10 amps
115What is the wave shape of the x-axis input of a traversing oscilloscope image?.
1. ARectangular.
2. BTriangular.
3. CSquare
116In a purely resistive AC circuit, the current vector is.
1. A +90° out of phase with the voltage vector.
2. Bin phase with the voltage vector.
3. C-90° out of phase with the voltage vector
117 When comparing the average values of an AC generator output, to the peak values.
1. Aaverage voltage = 0.707 * peak voltage.
2. Baverage voltage = 0.63 * peak voltage.
3. Caverage voltage = same as the peak voltage
118 A parallel circuit at resonance has.
1. Amaximum impedance.
2. Bzero impedance.
3. Cminimum impedance.
119A 10 ohm resistor has a 14.14 V peak drop across it. What power is dissipated?.
1. A10 W.
2. B19.99 W.
3. C1.414 W.
120If a 1 ohm circuit produces a 50 W output, the phase angle is.
1. A45°.
2. B0°.
3. C90°.
121What does a rectifier do?.
1. AChanges alternating current into direct current.
2. BReduces voltage.
3. CChanges direct current into alternating current.
122The ratio between apparent power and true power is the.
1. Apower rating.
2. Bpower factor.
3. Cefficiency
123One advantage of using AC electrical power in aircraft is.
1. Athe greater ease in stepping the voltage up or down.
2. BAC electrical motors can be reversed while DC motors cannot.
3. Cthe effective voltage is 1.41 times the maximum instantaneous voltage; therefore, less power input is required.
124Unless otherwise specified, any values given for current or voltage in an AC circuit are assumed to be.
1. Aeffective values.
2. Binstantaneous values.
3. Cmaximum values.
125Which aircraft circuit would be most likely to use frequency wild 200V AC?.
1. AHydraulic pump.
2. BWindscreen heating.
3. CStandby compass.
126One 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.
1. ADC by means of transformers.
2. BDC by means of inverters.
3. CAC by means of transformers.
127How 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?.
1. A1 ampere.
2. B25.23 amperes.
3. C1.11 amperes.
128Frequency (Hz) is the number of cycles per.
1. Aminute.
2. Bsecond.
3. Crevolution.
129The frequency of a power wave in an AC resistance circuit is.
1. Ahalf the frequency for voltage and current.
2. Bthe same as the frequency for voltage and current.
3. Ctwice the frequency for voltage and current
130In an AC circuit, the effective voltage is.
1. Aless than the maximum instantaneous voltage.
2. Bequal to the maximum instantaneous voltage.
3. Cgreater than the maximum instantaneous voltage.
131Which wave form is stepped positive and negative with unequal length sides?.
1. ARectangular wave.
2. BTrapezoidal wave.
3. CSaw tooth wave.
132The value of an AC sine wave that will give an equivalent heating effect in a DC resistor is the.
1. Apeak value.
2. BRMS value.
3. Caverage value.
133The peak factor for a sine wave is.
1. A1.11.
2. B0.707.
3. C1.414.
134An integrated step input at unequal time base produces.
1. Aa sine wave.
2. Ba square wave.
3. Ca saw tooth wave.
135The mark-to-space ratio of the waveform shown is.
1. AA to D / D to E.
2. BD to E / D to C.
3. CA to B / B to C.
136Form Factor for a sine wave AC output is.
1. A1.1.
2. B1.414.
3. C0.707.
137 A sine wave of RMS value 7.07 volts has a peak to peak value of.
1. A20.0 volts.
2. B10.0 volts.
3. C0.707 volts.
138The true power in an AC circuit is given by.
1. Avolts * amps.
2. BPF * volts * amps.
3. Cvoltmeter reading * PF
139The average value of 100 volts peak AC is.
1. A70.7 volts.
2. B141.4 volts.
3. C63.7 volts.
140The RMS value of 200 volts peak to peak is.
1. A127.4 volts.
2. B70.7 volts.
3. C141.4 volts.
141The power factor of an AC circuit is the.
1. Acosine of the phase angle.
2. Btangent of the phase angle.
3. Csine of the phase angle.
142The Form Factor of an AC waveform can be found by.
1. ARMS value divided by the average value.
2. Baverage value divided by the RMS value.
3. Caverage value times the RMS value
143A differentiator has a time constant which is.
1. Along.
2. Bequal to the input pulse.
3. Cshort.
144If the frequency is increased in an AC circuit of pure resistance, the effect is.
1. Anothing.
2. Bdecreased resistance.
3. Cincreased resistance.
145What sort of wave would be used in a CR oscilloscope to control sweep?.
1. ASquare.
2. BSine wave.
3. CSawtooth.
146If an AC sine wave has an RMS value of 5V its peak value is.
1. A6.37 V.
2. B7.07 V.
3. C14.14 V
147Apparent power in an AC circuit is found by.
1. AV * I * cosØ.
2. BV * I * sinØ.
3. CV * I.
148A sine wave has a periodic time of 0.5 milliseconds, what is its frequency?.
1. A200 Hz.
2. B2Khz.
3. C20Khz.
149Phase angle is.
1. Athe cosine of the peak value of an ac voltage.
2. Bthe difference in degrees of rotation between 2 alternating voltages or currents or a voltage and a current.
3. Cthe difference in degrees between the positive and negative parts of an AC sine wave.
150The impedance of an AC circuit is measured in.
1. Aohms.
2. Bkilovolt-amperes.
3. Camperes.
151What happens to the current in a series resistive resonant circuit?.
1. AIt is maximum.
2. BIt is minimum.
3. CIt is zero
152A circuit has 115 V RMS, 2.5A at 60 degrees, what is the power dissipated?.
1. A79 W.
2. B300 VA.
3. C143 W.
153In a resonant parallel circuit, current is.
1. Azero.
2. Bminimum.
3. Cmaximum.
154Power factor is.
1. Asin theta.
2. Btan theta.
3. Ccos theta.
155Peak factor in a standard AC circuit is.
1. A1.414 times max. value of applied voltage.
2. B1.11 times max. value of applied voltage.
3. C0.707 time max. value of applied voltage.
156The controlling wave in a CRT is.
1. Asquare.
2. Bsawtooth.
3. Csinusoidal.
157 A wave form having equal amplitude and time base is a.
1. Arectangular.
2. Bsawtooth.
3. Csquare waveform.
158The Sine wave signals of a circular time base are.
1. Ain phase.
2. Bphase separated by 90°.
3. Cphase separated by 180°
159A differentiator has a time constant that will give.
1. Aa long pulse.
2. Ba short pulse.
3. Ca continuous output
160What is the power factor in a purely resistive circuit?.
1. AEqual to 1.
2. BLess than 1 but greater than zero.
3. CGreater than 1.
161In an A.C circuit, what happens if frequency is reduced?.
1. AInductive elements may be damaged.
2. BCapacitive elements may be damaged.
3. CThere will be no effect
162What is the relationship between the voltage and the current in an A.C circuit containing resistance and inductance?.
1. ACurrent lags voltage by 90°.
2. BCurrent lags voltage by up to 90°.
3. CCurrent leads voltage by up to 90°.
163In this circuit.
1. Acurrent = voltage.
2. Bcurrent lags voltage.
3. Ccurrent leads voltage
164Power factor relates to.
1. Ahorsepower and Watts.
2. BKW and KVAR.
3. Ctrue power and apparent power.
165If current lags voltage by 90°, the circuit is.
1. Aresistive.
2. Bcapacitive.
3. Cinductive
166What does the following circuit represent?.
1. ALow pass filter.
2. BDifferentiator.
3. CIntegrator
167 A low frequency supply.
1. Awill make the circuit operate faster due to the reduced impedance.
2. Bmay damage inductive components.
3. Cwill have no effect on inductive components
168In a parallel R, L, C circuit, the value of the capacitor is quadrupled, then the value of the impedance would.
1. Aremain the same.
2. Breduce.
3. Cincreased.
169In a capacitive circuit, if the frequency is increased.
1. Areactance remains the same.
2. Bimpedance increases.
3. Cthe current increases
170In the circuit shown, what happens to the total circuit impedance if L is tripled?.
1. AReduces.
2. BIncreases.
3. CRemains the same.
171In a tuned circuit at resonance, the circuit will be.
1. Aresistive.
2. Bcapacitive.
3. Cinductive.
172A 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.
1. A31.42 ohms.
2. B62.84 ohms.
3. C6.284 ohms.
173In a vector diagram showing the magnitude and direction of the inductance, capacitance and resistance in an AC circuit.
1. Athe inductive and capacitance reactance would be additive with the resistance subtractive.
2. Bit is impossible to show values of this kind using vectors.
3. Cthe inductive reactance would be in opposition to the capacitive reactance and resistance at 90 degrees.
174At resonant frequency the phase difference between the voltage and current of an AC supply feeding an inductive and capacitive network is.
1. A90 degrees.
2. B0 degrees.
3. C180 degrees
175An increase in which of the following factors will cause an increase in the inductive reactance of a circuit?.
1. AInductance and frequency.
2. BResistance and capacitive reactance.
3. CResistance and voltage.
176When a circuit with a series inductance and capacitance is at resonant frequency.
1. Athe current in the circuit decreases.
2. Bthe impedance of the circuit is such that the voltage is in phase with the current.
3. Cthe impedance of the circuit is such that the voltage leads the current by exactly 90 degrees.
177 A pure capacitor, inductor and resistor are connected in series and the voltage drops across each are 10V and the total current flowing in the circuit is 1A. How much true power is the circuit consuming?.
1. A30VA.
2. B30W.
3. C10W.
178If a capacitor 1µF and an inductor 10mH are connected in parallel what is their approximate resonant frequency?.
1. A1.6 kHz.
2. B62 Hz.
3. C3.2 MHz.
179Current in an inductive circuit will.
1. Alag voltage.
2. Blead voltage.
3. Cbe at unity
180The impedance of a series tuned circuit at resonance is.
1. Azero.
2. Bminimum.
3. Cmaximum
181In an inductive resistive circuit, 1 amp flows from a supply of 100V dissipating 50 Watts of power. The phase angle is.
1. A60°.
2. B90°.
3. C45°.
182In the circuit shown, impedance will be.
1. A5 ohms.
2. B9 ohms.
3. C7 ohms
183In the circuit shown, if the frequency is increased from zero to resonant frequency, the circuit current would.
1. Aincrease.
2. Bdecrease.
3. Cstay the same.
184The true power developed in this circuit is.
1. A20W.
2. B50W.
3. C12W.
185In a series LCR circuit at resonance, R = 100 ohms, L and C are each 10 ohms. The total impedance is.
1. Azero ohms.
2. B100 ohms.
3. C30 ohms
186In a high Q parallel resonant circuit, what happens to impedance if capacitance is increased by a factor of 4?.
1. AIt increases by factor of 4.
2. BIt reduces by 75%.
3. CIt remains the same
187A parallel circuit at resonance has its impedance at a.
1. Amaximum.
2. Bzero.
3. Cminimum.
188The formula for impedance in a series circuit is the root of.
1. AR2 + (XC-XL)2 .
2. BR2 -(XL-XC)2 .
3. CR2 + (XL-XC)2 .
189 In this circuit applied voltage is.
1. AV = IXL.
2. BV = I/R.
3. CV = IXC.
190In a parallel LCR circuit, if the capacitance is increased by 4 times, what happens to the impedance of the capacitor?.
1. Aincreases by 4 times.
2. Bremains the same.
3. Cdecreases by 75%.
191If the frequency to a capacitor increases, the current through it.
1. Adecreases.
2. Bincreases.
3. Cis zero
192If in a electrical circuit there is a difference between the capacitive reactance and the inductive reactance, what would the power factor of the circuit be?.
1. AMore than unity.
2. BLess than unity.
3. CUnity.
193In a Series LC circuit if the value of the capacitance is increased then the power factor will be.
1. Agreater than 1.
2. Bless than 1.
3. Cequal to 1.
194What is the current in the circuit with a resistance of 8 ohms, inductive reactance of 12 ohms, capacitive reactance of 18 ohms with 20 volts applied across it?.
1. A10 amps.
2. B1 amp.
3. C2 amps
195A circuit containing a resistor, capacitor and inductor where resonant frequency is met, what will the impedance of the circuit be?.
1. AMaximum.
2. BResistance across the resistor.
3. CZero
196How many turns does the secondary winding of a 2:1 step-up transformer have?.
1. ALess than primary.
2. BMore than primary.
3. CLess turns but with thicker wire.
197To reduce eddy currents in a transformer you would.
1. Aincrease the thickness of laminations in the magnetic core.
2. Breduce the number of turns on the primary winding.
3. Creduce the thickness of laminations in the magnetic core
198A 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?.
1. A115V.
2. B346V.
3. C200V
199 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?
1. A205 amps.
2. B4.5 amps.
3. C9 amps.
200A Transformer has 4500 secondary turns and 750 primary turns. Its turns ratio is.
1. A1:6.
2. B1/6.
3. C6:1.

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Description: Quiz on Física 3, created by oriol arrufat on 20/10/2018.
Author: oriol arrufat
Language: English
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