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Q. No.The primary and secondary coils of a transformer have \(50\) and \(1500\) turns respectively. If the magnetic flux \(\phi\) 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
Subtopic: Transformer |
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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 |
Subtopic: Transformer |
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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
Subtopic: Power factor |
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In the network shown below what is the reading of the AC voltmeter?
1. Zero
2. \(100\text{ V}\)
3. \(200\text{ V}\)
4. \(500\text{ V}\)
1. Zero
2. \(100\text{ V}\)
3. \(200\text{ V}\)
4. \(500\text{ V}\)
Subtopic: Different Types of AC Circuits |
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The power factor of the given circuit is:
| 1. | \(1 \over 2\) | 2. | \(1 \over \sqrt2\) |
| 3. | \(\sqrt3 \over 2\) | 4. | \(0\) |
Subtopic: Power factor |
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The power factor of a series \(LCR\) circuit in resonance condition is:
| 1. | zero | 2. | \(\dfrac{1}{2}\) |
| 3. | \(\dfrac{1}{\sqrt{2}}\) | 4. | \(1\) |
Subtopic: Power factor |
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What is the instantaneous power of a resistor having resistance \(R\) across an AC supply of \(E= E_0\sin(\omega t)\)?
| 1. | \(\dfrac{E_{0}^{2}}{R} \sin^{2}\omega t\) | 2. | \(\dfrac{E_{0}^{2}}{R}\cos^{2}\omega t\) |
| 3. | \(\dfrac{E_{0}^{2}}{R}\) | 4. | \(\text{zero}\) |
Subtopic: Power factor |
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In a step-up transformer, the turn ratio is \(1:20\). The resistance of \(100~\Omega\) connected across the secondary is drawing a current of \(2~\text{A}\).
What are the primary voltage and current respectively?
1. \(100~\text{V}, 0.5~\text{A}\)
2. \(200~\text{V},10~\text{A}\)
3. \(10~\text{V}, 40~\text{A}\)
4. \(10~\text{V}, 20~\text{A}\)
Subtopic: Transformer |
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Voltage and current in an AC circuit are given by \(V=5\sin\left (100\pi t-\dfrac{\pi }{6}~ \right)~\text{V}\) and \(I=4\sin\left (100\pi t+\dfrac{\pi }{6}~\right)~\text{A}.\)
Hence:
Hence:
| 1. | The voltage leads the current by \(30^{\circ}\). |
| 2. | The current leads the voltage by \(30^{\circ}\). |
| 3. | The current leads the voltage by \(60^{\circ}\). |
| 4. | The voltage leads the current by \(60^{\circ}\). |
Subtopic: RMS & Average Values |
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An alternating voltage (in volts) given by \(V=200\sqrt{2}\sin100t\) is connected to a \(1~\mu \text{F}\) capacitor through an \(\text{AC}\) ammeter. The reading of the ammeter will be:
| 1. | \(10~\text{mA}\) | 2. | \(20~\text{mA}\) |
| 3. | \(40~\text{mA}\) | 4. | \(80~\text{mA}\) |
Subtopic: Different Types of AC Circuits |
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