Q. No.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: Â Transformer |
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If the primary side of a transformer is connected with \(230~\text{V},~50~\text{Hz}~\text{AC}\) supply and the ratio of the number of turns of primary to the secondary winding is \(10:1.\) The load resistance at the secondary coil is \(46~\Omega\), then the power output of the secondary windings is:
1. \(11.5~\text{watt}\)
2. \(13~\text{watt}\)
3. \(16~\text{watt}\)
4. \(15.6~\text{watt}\)
1. \(11.5~\text{watt}\)
2. \(13~\text{watt}\)
3. \(16~\text{watt}\)
4. \(15.6~\text{watt}\)
Subtopic: Â Transformer |
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The core of the transformer is laminated so that:
1. the copper loss is minimized.
2. the eddy current loss is minimized.
3. the rusting of the core is stopped.
4. the change in flux is increased.
1. the copper loss is minimized.
2. the eddy current loss is minimized.
3. the rusting of the core is stopped.
4. the change in flux is increased.
Subtopic: Â Transformer |
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A transformer has an efficiency of \(80\text{%}.\) It works at \(40\) kW and \(100\) V. If the secondary voltage is \(240\) V, the current in the secondary coil is nearly:
1. \(40\) A
2. \(133.3\) A
3. \(86.7\) A
4. \(112\) A
1. \(40\) A
2. \(133.3\) A
3. \(86.7\) A
4. \(112\) A
Subtopic: Â Transformer |
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A step-down transformer operates on \(2\) kV line. The ratio of the primary winding to the secondary winding is \(20:1\). Assuming \(100\%\) efficiency, the secondary voltage \(V_2\) is:
1. \(100~\text V\)
2. \(110~\text V\)
3. \(200~\text V\)
4. \(250~\text V\)
1. \(100~\text V\)
2. \(110~\text V\)
3. \(200~\text V\)
4. \(250~\text V\)
Subtopic: Â Transformer |
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An ideal transformer has \(100\) turns in the primary coil and carries a \(5\) A current. To achieve a \(1600\) V output with a \(2\) kW power output, the number of turns in the secondary coil must be:
1. \(100\)
2. \(200\)
3. \(300\)
4. \(400\)
1. \(100\)
2. \(200\)
3. \(300\)
4. \(400\)
Subtopic: Â Transformer |
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A transformer is used to light \(140\) watts \(24\) volt lamp from \(240\) volt AC mains; the current in the main cable is \(0.7\) amp. The efficiency of the transformer is:
1. \(63.8\%\)
2. \(84\%\)
3. \(83.3\%\)
4. \(48\%\)
1. \(63.8\%\)
2. \(84\%\)
3. \(83.3\%\)
4. \(48\%\)
Subtopic: Â Transformer |
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A step-down transformer is employed to reduce the main supply of AC from \(220~\text{V}\) to \(11~\text{V}\). If the primary coil draws a current of \(5~\text{A}\) and the secondary supplies a current of \(90~\text{A}\), then the efficiency of the transformer is:
1. \(10\%\)
2. \(95\%\)
3. \(90\%\)
4. \(80\%\)
Subtopic: Â Transformer |
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The primary to secondary turns-ratio \({\large\frac{N_P}{N_S}}=10,\) for a transformer. If a primary \(\text{AC}\) voltage of \(100~\text V\) RMS is applied at the primary, the \(\text{AC}\) output voltage at secondary will be (RMS):
1. \(100~\text V\)
2. \(1000~\text V\)
3. \(10~\text V\)
4. \(10^4~\text V\)
1. \(100~\text V\)
2. \(1000~\text V\)
3. \(10~\text V\)
4. \(10^4~\text V\)
Subtopic: Â Transformer |
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A transformer has \(50\) turns in the primary coil and \(100\) turns in the secondary coil. If the primary is connected to a \(200~\mathrm{V}\) AC supply, what will be the voltage in the secondary coil?
| 1. | \(100~\mathrm{V}\) | 2. | \(400~\mathrm{V}\) |
| 3. | \(90~\mathrm{V}\) | 4. | \(360~\mathrm{V}\) |
Subtopic: Â Transformer |
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