Q.1
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.2
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.3
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.4
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.5
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.6
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.7
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.8
The period of a sine wave is ___________ seconds. Its frequency is
  • 20 Hz
  • 30 Hz
  • 40 Hz
  • 50 Hz
Q.9
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
  • None of the above
  • 220/v³ V
Q.10
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.11
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.12
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.13
In a series resonant circuit, the impedance of the circuit is
  • Minimum
  • Maximum
  • Zero
  • None of the above
Q.14
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.15
The power factor of a D.C. circuit is always
  • Less than unity
  • Unity
  • Greater than unity
  • Zero
Q.16
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.17
At __________ frequencies the parallel R-L circuit behaves as purely resistive.
  • Low
  • Very low
  • High
  • Very high
Q.18
At __________ frequencies the parallel R-L circuit behaves as purely resistive.
  • Low
  • Very low
  • High
  • Very high
Q.19
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.20
The double energy transient occur in the
  • Purely inductive circuit
  • R-L circuit
  • R-C circuit
  • R-L-C circuit
Q.21
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.22
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.23
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.24
A heater is rated asV,kW, A.C. The valueV refers to
  • Average voltage
  • r.m.s. voltage
  • Peak voltage
  • None of the above
Q.25
The phase difference between voltage and current wave through a circuit element is given as 30°. The essential condition is that
  • Both waves must have same frequency
  • Both waves must have identical peak values
  • Both waves must have zero value at the same time
  • None of the above
Q.26
Capacitive reactance is more when
  • Capacitance is less and frequency of supply is less
  • Capacitance is less and frequency of supply is more
  • Capacitance is more and frequency of supply is less
  • Capacitance is more and frequency of supply is more
Q.27
Time constant of a capacitive circuit
  • Increases with the decrease of capacitance and decrease of resistance
  • Increases with the decrease of capacitance and increase of resistance
  • Increases with the increase of capacitance and decrease of resistance
  • Increase with increase of capacitance and increase of resistance
Q.28
A pure capacitor connected across an A.C. voltage consumedW. This is due to
  • The capacitive reactance in ohms
  • The current flowing in capacitor
  • The size of the capacitor being quite big
  • The statement is incorrect
Q.29
In a parallel R-C circuit, the current always _________the applied voltage
  • Lags
  • Leads
  • Remains in phase with
  • None of the above
Q.30
Skin effect occurs when a conductor carries current at _________ frequencies.
  • Very low
  • Low
  • Medium
  • High
0 h : 0 m : 1 s