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Q. No.An alternating emf of \(V=20\) V \(\mathrm{sin}(100\pi ~\text{s}^{-1}.t)\) is applied to an inductor and the peak current through the inductor is observed to be \(\dfrac{20}{\pi}\) A. The inductance is:
1.
\(\dfrac{1}{10}\) H
2.
\(\dfrac{1}{100}\) H
3.
\(\dfrac{1}{1000}\) H
4.
\(\dfrac{1}{10^4}\) H
Subtopic: Ā RMS & Average Values |
Ā 85%
Level 1: 80%+
Hints
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R):
In the light of the above statements choose the correct answer from the options given below:
| Assertion (A): | A transformer cannot work on DC supply. |
| Reason (R): | DC changes neither in magnitude nor in direction. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | Both (A) and (R) are False. |
Subtopic: Ā Transformer |
Ā 89%
Level 1: 80%+
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A capacitor has a capacitance of \(C\) and reactance of \(X.\) If both capacitance and frequency are doubled, the new reactance will be:
| 1. | \(4X\) | 2. | \(X/2\) |
| 3. | \(X/4\) | 4. | \(2X\) |
Subtopic: Ā Different Types of AC Circuits |
Ā 84%
Level 1: 80%+
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A series \(LCR\) circuit is operated at resonance.
| Statement I: | The power transferred to the resistor is the maximum |
| Statement II: | The current in the circuit is maximum. |
| 1. | Statement I is correct and Statement II is incorrect. |
| 2. | Statement I is incorrect and Statement II is correct. |
| 3. | Both Statement I and Statement II are correct. |
| 4. | Both Statement I and Statement II are incorrect. |
Subtopic: Ā Different Types of AC Circuits |
Ā 86%
Level 1: 80%+
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The rms value of conduction current in a parallel plate capacitor is \(6.9~\mu \text{A}\). The capacity of this capacitor, if it is connected to \(230\) V AC supply with an angular frequency of \(600\) rad/s, will be:
1. \(5~\text{pF}\)
2. \(50~\text{pF}\)
3. \(100~\text{pF}\)
4. \(200~\text{pF}\)
1. \(5~\text{pF}\)
2. \(50~\text{pF}\)
3. \(100~\text{pF}\)
4. \(200~\text{pF}\)
Subtopic: Ā Different Types of AC Circuits |
Ā 79%
Level 2: 60%+
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A transformer operating at a primary voltage of \(8\) kV and secondary voltage of \(160\) V serves a load of \(80\) kW. Assuming the transformer to be ideal with purely resistive load and working on unity power factor, the loads in the primary and secondary circuit would be:
| 1. | \(800~\Omega\) and \(1.06~\Omega\) | 2. | \(10~\Omega\) and \(500~\Omega\) |
| 3. | \(800~\Omega\) and \(0.32~\Omega\) | 4. | \(1.06~\Omega\) and \(500~\Omega\) |
Subtopic: Ā Transformer |
Ā 79%
Level 2: 60%+
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An alternating emf \(E = 440\sin(100\pi t)\) is applied to a circuit containing an inductance of \(\frac{\sqrt{2}}{\pi}\) H. If an AC ammeter is connected to the circuit, its reading will be:
1. \(4.4\) A
2. \(1.55\) A
3. \(2.2\) A
4. \(3.11\) A
1. \(4.4\) A
2. \(1.55\) A
3. \(2.2\) A
4. \(3.11\) A
Subtopic: Ā Different Types of AC Circuits |
Ā 73%
Level 2: 60%+
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A resistance of \(40~\Omega\) is connected to a source of alternating current rated \(220\) V, \(50\) Hz. The time taken by the current to change from its maximum value to the RMS value is:
1. \(2.5\) ms
2. \(1.25\) ms
3. \(2.5\) s
4. \(0.25\) s
1. \(2.5\) ms
2. \(1.25\) ms
3. \(2.5\) s
4. \(0.25\) s
Subtopic: Ā Different Types of AC Circuits |
Ā 71%
Level 2: 60%+
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A capacitor is in series with a resistor of \(30~\Omega\) and is connected to a \(220~\text V\) AC line. The reactance of this capacitor is \(30~\Omega.\) What is the phase angle between the current and the supply voltage?
1. \(-30^\circ\)
2. \(-45^\circ\)
3. \(-60^\circ\)
4. \(90^\circ\)
1. \(-30^\circ\)
2. \(-45^\circ\)
3. \(-60^\circ\)
4. \(90^\circ\)
Subtopic: Ā Different Types of AC Circuits |
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An AC voltage \(V\) is applied across an impedance, that gives rise to a current \(I.\) The angle between \(V\) and \(I\) is \(\theta.\) The power loss is:
1. \(VI \cos\theta\)
2. \(VI \sin\theta\)
3. \(VI/ \cos\theta\)
4. \(VI/ \sin\theta\)
1. \(VI \cos\theta\)
2. \(VI \sin\theta\)
3. \(VI/ \cos\theta\)
4. \(VI/ \sin\theta\)
Subtopic: Ā Power factor |
Ā 89%
Level 1: 80%+
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