Q.1
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
0 h : 0 m : 1 s