A sinusoidal voltage V(t) = 100 sin(500t) is applied across a pure inductance of L= 0.02 H. The current through the coil is :
1. 10 cos (500 t)
2. -10 cos(500t)
3. 10 sin (500t)
4. -10 sin (500t)
For the LCR circuit fig., shown here the current is observed to lead the applied voltage. An additional capacitor C1, when joined with capacitor C present in the circuit makes the power factor of the circuit unity. The capacitor C must have been connected in :
1. Series with C and has a magnitude
2. Series with C and has a magnitude
3. Parallel with C and has a magnitude
4. Parallel with C and has a magnitude
The AC voltage across a resistance can be measured using a :
1. Potentiometer
2. Moving coil galvanometer
3. Moving magnet galvanometer
4. hot wire voltmeter
An arc lamp requires a direct current of 10 A at 80 V function. It is connected to 220 V (rms), 50 Hz AC supply, the series inductor needed for it to work is close to :
1. 80 H
2. 0.08 H
3. 0.044 H
4. 0.065 H
A sinusoidal voltage of peak value 283 V, angular frequency 320/s is applied to a series LCR circuit. Given that R = 5 , L = 25 mH and C = 1000 . The total impedance and phase difference between the voltage across the source and the current will respectively be :
1. 10 and
2. 7 and 45
3. 10 and
4. 7 and
When the rms voltages are measured respectively across the inductor, the capacitor C and the resistor R in a series LCR circuit connected to an AC source, it is found that the ratio . If the rms voltage of the AC source is 100 V, then is close to :
1. 50 V
2. 100 V
3. 70 V
4. 90 V
For an RLC circuit driven through the voltage of amplitude and frequency the current exhibits resonance. The quality factor Q is given by:
1.
2.
3.
4.
If an ideal capacitor of capacitance 0.2 is charged to a potential difference of 10 V. The charging battery is then disconnected. The capacitor is then connected to an ideal inductor of self inductance 0.5 mH. The current at a time when the potential difference across the capacitor is 5V, is :
1. 0.34 A
2. 0.25 A
3. 0.17 A
4. 0.15 A
A power transmission line feeds input power at 2300V to a step down transformer with its primary windings having 4000 turns, giving the output power at 230 V. If the current in the primary of the transformer is 5A, and its efficiency is 90%, the output current would be:
1. 50 A
2. 45 A
3. 25 A
4. 20 A
At a moment (t = 0), when the charge on capacitor C1 is zero, the switch is closed. If I0 be the current through inductor at t = 0 , for t > 0
1. maximum current through inductor equals I0/2.
2. maximum current through inductor equals
3. maximum charge on
4. maximum charge on
A circuit consists of a capacitor and a resistor having resistance R = 220 Ω connected in series. When an alternating e.m.f. of peak voltage V0 = 220 V is applied to the circuit, the peak current in steady state is observed to be I0 = 1A. The phase difference between the current and the voltage is
1. 30°
2. 45°
3. 60°
4. 90°
By what factor the reactance in an AC circuit should be increased so that the power factor changes from (1/2) to (1/4)?
1. 2
2.
3. 3
4. none