Important MCQs of AC Circuit – 4
In this post, some of the important questions of AC Circuits are given, it includes angle between voltage vector and current vector in the resistor circuit, inductor circuit and capacitor circuit, power loss in pure inductor, power loss in pure capacitor, power loss in pure resistor, voltage across inductor, leg circuit, lead circuit, equation of capacitive reactance.
AC Circuit MCQs: 61 to 65
61 The voltage vector and current vector in the pure resistive circuit attains ______value at same time.
( a )Zero
( b )Positive
( c )Negative
( d )All of the above
Correct Answer ( d ): All of the above
The angle between voltage vector and current vector in the pure resistive circuit is zero therefore it attains zero value, maximum value and all other value at given angle is same.
62 The power loss in the pure inductive circuit is
( a )100 watt
( b )10 watt
( c )1 watt
( d )Zero watt
Correct Answer ( d ): Zero watt
Power loss in the pure inductive circuit and pure capacitive circuit is zero watt because there is no resistance in the pure inductive circuit and pure capacitive circuit.
63 The voltage across inductor at any instant is given by
( a )L × ( dv / dt )
( b )L × ( di / dt )
( c )L / ( dv / dt )
( d )∫ vdt
Correct Answer ( b ): L × ( di / dt )
64 The current vector lags behind by voltage vector in the pure inductive circuit is
( a )π
( b )π / 2
( c )π / 3
( d )π / 6
Correct Answer ( b ): π / 2
The angle between voltage vector and current vector always 90 degree in the pure inductive circuit and pure capacitive circuit.
65 The inductive reactance is given by
( a )ωL
( b )ω2L
( c )ω2LC
( d )πfL
Correct Answer ( a ): ωL
XL = 2πfL
AC Circuit MCQs: 66 to 70
66 The inductive reactance increases with increase in the
( a )Voltage
( b )Current
( c )Impedance
( d )Frequency
Correct Answer ( d ): Frequency
XL = 2πfL, therefore as the frequency increases, inductive reactance also increases.
67 The voltage vector ______ the current vector in the capacitive circuit.
( a )Lag
( b )Lead
( c )Is in phase with
( d )Any of the above
Correct Answer ( a ): Lag
The current vector leads voltage vector in the capacitor circuit.
68 The capacitive reactance is given by
( a )ωC
( b )ω2C
( c )1 / ωC
( d )1 / ω2C
Correct Answer ( c ): 1 / ωC
69 Which of the following parameter does not affect by the variation of frequency?
( a )XL
( b )XC
( c )R
( d )XL ~ XC
Correct Answer ( c ): R
There is no effect on frequency on resistance whereas as the frequency increase, capacitive reactance decreases and inductive reactance increases.
70 The power loss in the pure capacitive circuit is
( a )Zero watt
( b )10 watt
( c )50 watt
( d )230 watt
Correct Answer ( a ): Zero watt
The power loss in the pure capacitive and pure inductive circuit is always zero.
AC Circuit MCQs: 71 to 75
71 The unit of inductive reactance is
( a )Ohm–1
( b )Henry
( c )Siemens
( d )Ohm
Correct Answer ( d ): Ohm
The unit of capacitive reactance and inductive reactance is ohm.
72 The unit of capacitive reactance is
( a )Ohm–1
( b )Micro – farad
( c )Siemens
( d )Ohm
Correct Answer ( d ): Ohm
The unit of capacitive reactance and inductive reactance is ohm.
73 The phase difference between voltage vector and current vector in a pure capacitive circuit is
( a )0o
( b )30o
( c )90o
( d )180o
Correct Answer ( c ): 90o
The phase difference between voltage vector and current vector always 90 degree in the pure capacitor and pure inductive circuit.
74 The voltage vector leads current vector by 60o if it is a
( a )Pure resistance circuit
( b )Pure inductive circuit
( c )Pure capacitive circuit
( d )Capacitive
Correct Answer ( d ): Capacitive
The current vector always leads voltage vector by few angle in the capacitor circuit.
75 The power loss in the capacitive circuit is
( a )VI
( b )Vmax Imax / √2
( c )VI / √ 2
( d )Zero
Correct Answer ( a ): VI
Equation of power loss in the capacitor is VI, however power loss in pure capacitor is zero.
Advance Topic: Power Loss in Capacitor
AC Circuit MCQs: 76 to 80
76 Identify the type of circuit for following equations: V = Vm sin ωt and I = Im sin ( ωt – π / 3 )
( a )Resistive
( b )Inductive
( c )Capacitive
( d )Any of the above
Correct Answer ( b ): Inductive
As the current vector legs voltage vector by π / 3 angle, it is lagging circuit.
77 The dielectric loss in 10 µf pure capacitor is
( a )10 watt
( b )100 watt
( c )10 / √ 2 watt
( d )Zero
Correct Answer ( d ): Zero
Power loss in the pure capacitor is zero.
78 The practical capacitor internally consists of
( a )High resistance in parallel
( b )Low resistance in series
( c )Low resistance in parallel
( d )Either ( a ) or ( b )
Correct Answer ( d ): Either ( a ) or ( b )
The practical capacitor consists of capacitor is in series or parallel whereas the ideal capacitor has zero resistance is in parallel or series.
79 The RMS value of sinusoidal alternating voltage is equal to its value at an angle of
( a )180o
( b )90o
( c )45o
( d )0o
Correct Answer ( c ): 45o
80 The current vector leads voltage vector by 60o it is ______ circuit.
( a )Resistive
( b )Pure capacitive
( c )Pure inductive
( d )Capacitive
Correct Answer ( d ): Capacitive
The current vector always leads voltage vector in the capacitive circuit.
AC Circuit MCQs PDF
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