Power factor of an inductive circuit is usually improved by connecting capacitor to it in
Parallel
Series
Either A or B
None of the above
Q.2.
The effective resistance of an iron-cored choke working on ordinary supply frequency is more than its true resistance because of
Iron loss in core
Skin effect
Increase in temperature
Capacitive effect between adjacent coil turns
Q.3.
What will be the phase angle between two alternating waves of equal frequency, when one wave attains maximum value the other is at zero value?
0°
45°
90°
180°
Q.4.
The apparent power drawn by an A.C. circuit iskVA and active power is 8 kW. The reactive power in the circuit is
4 kVAR
6 kVAR
8 kVAR
16 kVAR
Q.5.
If a sinusoidal wave has frequency ofHz withA r.m.s. current which of the following equation represents this wave?
42.42 sin 314 t
60 sin 25 t
30 sin 50 t
84.84 sin 25 t
Q.6.
The r.m.s. value of half wave rectified sine wave isV. The r.m.s. value of full wave rectified AC. will be
282.8 V
141.4 V
111 V
100 V
Q.7.
The r.m.s. value of pure cosine function is
0.5 of peak value
0.707 of peak value
Same as peak value
Zero
Q.8.
The phosphors for which of the following pair areout of phase for VL, VC and VR?
VC and VR
VL and VR
VC and VL
None of the above
Q.9.
In an AC. circuit, a low value of kVAR compared with kW indicates
Low efficiency
High power factor
Unity power factor
Maximum load current
Q.10.
If two sinusoids of the same frequency but of different amplitudes and phase angles are subtracted, the resultant is
A sinusoid of the same frequency
A sinusoid of half the original frequency
A sinusoid of double the frequency
Not a sinusoid
Q.11.
The square waveform of current has following relation between r.m.s. value and average value.
r.m.s. value is equal to average value
r.m.s. value of current is greater than average value
r.m.s. value of current is less than average value
None of the above
Q.12.
The square waveform of current has following relation between r.m.s. value and average value.
r.m.s. value is equal to average value
r.m.s. value of current is greater than average value
r.m.s. value of current is less than average value
None of the above
Q.13.
The time constant of the capacitance circuit is defined as the time during which voltage
Falls to 36.8% of its final steady value
Rises to 38.6% of its final steady value
Rises to 63.2% of its final steady value
None of the above
Q.14.
The period of a sine wave is ___________ seconds. Its frequency is
20 Hz
30 Hz
40 Hz
50 Hz
Q.15.
In each of the three coils of a three phase generator, an alternating voltage having an r.m.s. value ofV is induced. Which of the following values is indicated by the voltmeters?
220 V
220 v3 V
220/v3 V
None of the above
Q.16.
The form factor is the ratio of
Peak value to r.m.s. value
r.m.s. value to average value
Average value to r.m.s. value
None of the above
Q.17.
In series resonant circuit, increasing inductance to its twice value and reducing capacitance to its half value
Will change the resonance frequency
Will change the maximum value of current at resonance
Will change the impedance at resonance frequency
Will increase the selectivity of the circuit
Q.18.
A pure inductance connected acrossV,Hz supply consumesW. This consumption can be attributed to
The big size of the inductor
The reactance of the inductor
The current flowing in the inductor
The statement given is false
Q.19.
In a series resonant circuit, the impedance of the circuit is
Minimum
Maximum
Zero
None of the above
Q.20.
Form Factor is the ratio of
Average value/r.m.s. value
Average value/peak value
r.m.s. value/average value
r.m.s. value/peak value
Q.21.
The power factor of a D.C. circuit is always
Less than unity
Unity
Greater than unity
Zero
Q.22.
In AC. circuits, laminated iron is invariably used in order to
Reduce eddy current loss
Increase heat radiation
Make assembly cheap and easier
Reduce circuit permeability
Q.23.
At __________ frequencies the parallel R-L circuit behaves as purely resistive.
Low
Very low
High
Very high
Q.24.
At __________ frequencies the parallel R-L circuit behaves as purely resistive.
Low
Very low
High
Very high
Q.25.
A phasor is
A line which represents the magnitude and phase of an alternating quantity
A line representing the magnitude and direction of an alternating quantity
A colored tag or band for distinction between different phases of a 3-phase supply
An instrument used for measuring phases of an unbalanced 3-phase load
Q.26.
The double energy transient occur in the
Purely inductive circuit
R-L circuit
R-C circuit
R-L-C circuit
Q.27.
Time constant of an inductive circuit
Increases with increase of inductance and decrease of resistance
Increases with the increase of inductance and the increase of resistance
Increases with the decrease of inductance and decrease of resistance
Increases with decrease of inductance and increase of resistance
Q.28.
Capacitive susceptance is a measure of
Reactive power in a circuit
The extent of neutralization of reactive power in a circuit
A purely capacitive circuit's ability to pass current
A purely capacitive circuit's ability to resist the flow of current
Q.29.
In the case of an unsymmetrical alternating current the average value must always be taken over
Unsymmetrical part of the wave form
The quarter cycle
The half cycle
The whole cycle
Q.30.
A heater is rated asV,kW, A.C. The valueV refers to
Average voltage
r.m.s. voltage
Peak voltage
None of the above
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