Q. No.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) |
The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux linked with the primary coils is given by \(\phi=\phi_0+4t\), where \(\phi\) is in webers, t is time in seconds, and \(\phi_0\) is a constant, the output voltage across the secondary coil is:
| 1. | 120 V | 2. | 220 V |
| 3. | 30 V | 4. | 90 V |
The primary winding of a transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of 20 V, 50 Hz. What will be the output of the secondary transformer?
| 1. | 200 V, 50 Hz |
| 2. | 2 V, 50 Hz |
| 3. | 200 V, 500 Hz |
| 4. | 2 V, 5 Hz |
If R and L are resistance and inductance of a choke coil and f is the frequency of current through it, then the average power of the choke coil is proportional to:
1. \(R ~\)
2. \(\frac{1}{f^2}\)
3. \(\frac{1}{L^2}\)
4. All of these
In the network shown below what is the reading of the a.c voltmeter?
1. Zero
2. 100 V
3. 200 V
4. 500 V
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