Q. No.In an ac circuit, the current is given by \(i=5\sin(100t-\frac{\pi}{2})\) and the ac potential is V = 200 sin(100t) volt.
The power consumption is:
1. 20 W
2. 40 W
3. 1000 W
4. 0
In an LCR circuit having L = 8.0 henry, C = 0.5 μF and R = 100 ohm in series, what is the resonance frequency?
1. 600 radian/sec
2. 600 Hz
3. 500 radian/sec
4. 500 Hz
A circuit consists of 3 ohms of resistance and 4 ohms of reactance. The power factor of the circuit is:
1. 0.4
2. 0.6
3. 0.8
4. 1.0
The power factor of a good choke coil is:
1. Nearly zero
2. Exactly zero
3. Nearly one
4. Exactly one
In a series LCR circuit, resistance \(R=10~\Omega\) and the impedance \(Z=20~\Omega\). The phase difference between the current and the voltage will be:
1. 30°
2. 45°
3. 60°
4. 90°
In the circuit shown in the figure, neglecting source resistance, the voltmeter and ammeter reading respectively will be:
1. 0 V, 3 A
2. 150 V, 3 A
3. 150 V, 6 A
4. 0 V, 8 A
An ac source of variable frequency f is connected to an LCR series circuit. Which of the following graphs represents the variation of the current I in the circuit with frequency f?
| 1. |  |
2. |  |
| 3. |  |
4. |  |
An inductor of \(20~\mathrm{mH},\) a capacitor of \(50~ \mu F,\) and a resistor of \(40~ \Omega\) are connected in series across a source of emf of \(V=10sin(340t).\) What will be the power loss in the AC circuit?
| 1. | \(0.67~ \mathrm{W}\) | 2. | \(0.78~ \mathrm{W}\) |
| 3. | \(0.89~ \mathrm{W}\) | 4. | \(0.46~ \mathrm{W}\) |
A step–down transformer transforms a supply line voltage of 2200 volt into 220 volt. The primary coil has 5000 turns. The efficiency and power transmitted by the transformer are 90% and 8 kilowatts respectively. How many turns are there in the secondary one?
| 1. | 5000 | 2. | 50 |
| 3. | 500 | 4. | 5 |
Match List I (expression for current) with List II (RMS value of current) and select the correct answer.
| List I | List II | ||
| (a) | \(I=I_0 \sin \omega t \cos \omega t\) | (i) | \(I_0\) |
| (b) | \(I=I_0 \sin \left(\omega t+\frac{\pi}{3}\right)\) | (ii) | \(I_0/\sqrt{2}\) |
| (c) | \(I_0(\sin \omega t+\cos \omega t)\) | (iii) | \(I_0e\) |
| (d) | \(I=I_0(e)\) | (iv) | \(I_0/2\sqrt{2}\) |
| A | B | C | D | |
| 1. | (iv) | (ii) | (i) | (iii) |
| 2. | (iv) | (ii) | (iii) | (i) |
| 3. | (ii) | (iv) | (iii) | (i) |
| 4. | (ii) | (iv) | (i) | (iii) |
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