A series-resonant circuit implies
1.zero pf and maximum current
2.unity pf and maximum current
3.unity pf and minimum current
4.zero pf and minimum current
Posted Date:-2022-10-09 15:21:35
Electrical power converted into heat due to the flow of an alternating current through an ohmic resistance is called the …….. power.
1.heating
2.true
3.reactive
4.apparent
Posted Date:-2022-10-09 12:24:42
If a series RLC circuit is excited by a voltage e = E sin ωt where LC < 1/ω2
1.current lags behind the applied voltage
2.current leads the applied voltage
3.voltage across L and C are equal
4.current is in phase with the applied voltage
Posted Date:-2022-10-09 12:44:19
In a series R-L-C circuit, the magnitude of resonance frequency can be changed by changing the value of
1.R only.
2.L only.
3.C only.
4.L or C.
Posted Date:-2022-10-09 15:19:36
In an ac circuit, the applied voltage and current drawn are represented as v = Vmax sin ωt and i = Imax sin (ωt + ϕ). The pf of the circuit is
1.sin Ï•
2.cos Ï• (lagging)
3.cos Ï• (leading)
4.none of these
Posted Date:-2022-10-09 12:37:27
In an R-L-C parallel circuit, the line current at resonance is
1.minimum at unity power factor
2.minimum at lagging pf
3.maximum at leading pf
4.maximum at lagging pf
Posted Date:-2022-10-09 15:26:12
In the 2 WM method of power measurement, one of the W.M. will show negative reading when the load pf angle is strictly
1.less than 30°
2.less than 60°
3.greater than 30°
4.greater than 60°
Posted Date:-2022-10-09 15:37:16
In the case of a delta connected load, if one resistor is removed, the power will become
1.zero
2.one-third
3. two-third
4.None of these
Posted Date:-2022-10-09 15:35:06
The power factor of an inductive circuit is usually improved by adding a capacitor to it in:
1. series
2.parallel
3.either in series or parallel
4.None of These
Posted Date:-2022-10-09 15:11:55
The RMS value of a sine wave is 100 A. Its peak value is
1.70.7 A
2.141 A
3.150 A
4.282.8 A
Posted Date:-2022-10-09 12:21:49
Under the condition of resonance in the RLC series circuit, the power factor of the circuit is
1.0.5 lagging
2.0.5 leading
3.unity
4.zero
Posted Date:-2022-10-09 15:09:43
16. In a 3-phase system, the EMFs are
1.30° apart
2.40° apart
3.90° apart
4.120° apart
Posted Date:-2022-10-09 15:30:55
A 100 W, 100 V bulb is to be supplied from 220 V, 50 Hz supply. Which of the following arrangements is preferable?
1.Additional pure inductance in series with lamp.
2.Additional resistance in series with the lamp.
3.Additional inductance and capacitance in series with the lamp.
4.None of the above
Posted Date:-2022-10-09 12:40:58
A 3-phase 6.6/0.4 kV transformer is to supply a load at 230 V. Its secondary should be connected in
1.star
2.delta
3.open-delta
4.series
Posted Date:-2022-10-09 15:34:07
A constant current of 2.8 A exists in a resistor. The RMS value of current is
1.2.8 A
2.about 2 A
3.1.4 A
4.Undefined
Posted Date:-2022-10-09 12:19:52
A current is said to be alternating when it changes in
1.magnitude only
2.direction only
3.both magnitude and direction
4.none of the above
Posted Date:-2022-10-09 12:12:52
A current is said to be direct current when its
1.magnitude remains constant with time
2.magnitude changes with time
3.direction changes with time
4.magnitude and direction changes with time
Posted Date:-2022-10-09 11:48:07
A lamp load is given a supply from 3-phase, 4-wire 230/400 V, A.C. supply system. If a 3- phase motor is now switched on across the same supply, then neutral current will
1.increase
2.decrease
3.remain unchanged
4.be unpredictable
Posted Date:-2022-10-09 15:39:55
A parallel resonant circuit can be employed
1.as a high impedance
2.to amplify certain frequencies
3.to amplify voltage
4. both high impedance and reject a small band of frequencies
Posted Date:-2022-10-09 15:29:04
A small capacitance is added to a highly inductive circuit,
1.the angle between voltage and current will increase
2.the pf will increase
3.the pf will decrease
4.the power drawn will decrease
Posted Date:-2022-10-09 15:08:39
A two-terminal black box contains a series combination of a resistor and an unknown two-terminal linear device. As soon as the battery is connected to the black box the current is found to be zero. The device is
1.an inductor
2.a capacitor
3.a resistor
4.an unknown
Posted Date:-2022-10-09 12:29:31
Average power in a purely resistive circuit is equal to
1.zero
2.product of average values of current and voltage
3.product of peak values of current and voltage
4.product of rms or effective values of current and voltage
Posted Date:-2022-10-09 12:25:43
Consider the following statements with respect to a series R-L-C circuit under resonance condition: All the applied voltage appears across R. There is no voltage across either L or C. The voltage across L and C equal and equal to their maximum values. Of these statements
1.1 alone is correct.
2.2 alone is correct.
3.1 and 3 are correct.
4.1 and 2 are correct.
Posted Date:-2022-10-09 15:18:20
If an alternating triangular voltage is applied to a resistor, the shape of the current waveform will be ……. waveform.
1.triangular
2.sawtooth
3.sinusoidal
4.square
Posted Date:-2022-10-09 12:26:23
In a series R-C circuit current …….. with the increase in frequency.
1.increases
2.decreases
3.remains unaltered
4.None of the above
Posted Date:-2022-10-09 12:39:29
In a series R-L circuit
1.voltage drops across R and L are in phase
2.voltage drop across L leads the voltage drop across R by 90°
3.voltage drop across L lags behind the voltage drop across R by 90°
4.voltage drops across R and L are in phase opposition
Posted Date:-2022-10-09 12:36:07
In ac circuits the power curve is a sine wave having
1.same frequency as that of voltage
2.double the frequency of the voltage
3.half the frequency of the voltage
4.none of the above
Posted Date:-2022-10-09 12:24:02
In the balanced 3-phase voltage system generated by a star connected alternator, VYB lags ER by
1.90 degrees
2.120 degrees
3.60 degrees
4.30 degrees
Posted Date:-2022-10-09 15:36:06
Q-factor of a coil is the measure of its
1.selectivity
2.retentivity
3.resistivity
4.self inductance
Posted Date:-2022-10-09 12:38:37
The angular frequency of an alternating quantity is a mathematical quantity obtained by multiplying the frequency f of the alternating quantity by a factor
1.Ï€/2
2.Ï€
3.2 π
4.4 π
Posted Date:-2022-10-09 12:19:00
The apparent power and active power is drawn are equal for an ac circuit of:
1.inductive type
2.capacitive type
3.resistive type
4.none of these
Posted Date:-2022-10-09 12:33:27
The Parallel R-C circuit behaves as a purely capacitive circuit at ………… frequencies.
1. very low
2. low
3.high
4.very high
Posted Date:-2022-10-09 15:14:35
The purely inductive circuit takes power from the ac mains when
1.both applied voltage and current increase
2.both applied voltage and current decrease
3.applied voltage decreases but current increases
4.applied voltage increases but current decreases
Posted Date:-2022-10-09 12:27:30
The quantity (12 + j9) represents the resistive and reactive components of the current drawn by an ac circuit. The phase angle between the applied voltage and the current is:
1.41.4°
2.53.13°
3.36.87°
4.48.6°
Posted Date:-2022-10-09 15:13:15
The ratio of effective value to average value is called the …. factor.
1.form
2.peak
3.average
4.Q-factor
Posted Date:-2022-10-09 12:20:41
The reactance offered by a capacitor to alternating current of frequency 50 Hz is 10 Ω. If the frequency is increased to 100 Hz, reactance becomes:
1.20 ohms
2.5 ohms
3.2.5 ohms
4.40 ohms
Posted Date:-2022-10-09 12:30:12
The source in the circuit shown is a sinusoidal source. The supply voltage across various elements is marked in the figure. The input voltage is
1.10 V
2.5 V
3.27 V
4.24 V
Posted Date:-2022-10-09 12:42:13
The standard supply frequency in India is
1.25 Hz
2.50 Hz
3.60 Hz
4.100 Hz
Posted Date:-2022-10-09 12:14:31
When a sinusoidal voltage is applied across R-L series circuit having R = XL, the phase angle will be:
1.90°
2.45° lag
3.45° leading
4.90° leading
Posted Date:-2022-10-09 12:34:23
When a sinusoidal voltage is applied across the R-L parallel circuit so that R = XL, the phase angle will be:
1.45° lag
2.45° leading
3.90° lag
4.90 leading
Posted Date:-2022-10-09 15:10:56
When the two quantities are in quadrature the phase angle between them will be
1.45° or π/4 radians
2.90° or π/2 radians
3.135° or 3π/4 radians
4.60° or π/3 radians
Posted Date:-2022-10-09 12:22:58
Which of the following statements associated with a purely capacitive circuit is not true?
1.Power consumed is zero.
2.Heat produced is zero.
3.Power factor is unity.
4.Work done is zero.
Posted Date:-2022-10-09 12:28:33
While measuring power in a three-phase load by 2 WM method. The reading of two wattmeters are equal and opposite, when
1.pf is unity
2.load is balanced
3.phase angle is between 60° and 30°
4.the load is purely inductive
Posted Date:-2022-10-09 15:38:29