Q. No.The core of a transformer is laminated because:
| 1. | Energy losses due to eddy currents may be minimized |
| 2. | The weight of the transformer may be reduced |
| 3. | Rusting of the core may be prevented |
| 4. | Ratio of voltage in primary and secondary may be increased |
Subtopic: Transformer |
90%
Level 1: 80%+
AIPMT - 2006
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Turn ratio of a step-up transformer is \(1: 25\). If current in load coil is \(2~\text{A}\), then the current in primary coil will be:
| 1. | \(25~\text{A}\) | 2. | \(50~\text{A}\) |
| 3. | \(0.25~\text{A}\) | 4. | \(0.5~\text{A}\) |
Subtopic: Transformer |
89%
Level 1: 80%+
AIPMT - 1998
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Given below are two statements:
| Assertion (A): | If the terminals of the primary of a transformer are connected across a battery then no emf is induced across the secondary in a steady state. |
| Reason (R): | The battery provides a steady current, so there is no change in flux linked with the secondary. |
| 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: Transformer |
89%
Level 1: 80%+
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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 |
84%
Level 1: 80%+
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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 |
85%
Level 1: 80%+
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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. \(5\)
1. \(5000\)
2. \(50\)
3. \(500\)
4. \(5\)
Subtopic: Transformer |
82%
Level 1: 80%+
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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 |
80%
Level 1: 80%+
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When a step-down transformer is connected to a \(2400\) volt line, the output load receives \(80\) amps of current. The ratio of the turns in the primary and secondary coils is \(20:1\). If transformer efficiency is \(100\%\), then the current flowing in the primary coil will be:
| 1. | \(1600\) A | 2. | \(20\) A |
| 3. | \(4\) A | 4. | \(1.5\) A |
Subtopic: Transformer |
78%
Level 2: 60%+
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In the transformer shown in the figure, the ratio of the number of turns of the primary to the secondary is \(\dfrac{N_1}{N_2}= \dfrac{1}{50}.\) If a voltage source of \(10~\text V\) is connected across the primary, then the induced current through the load of \(10~\text{k}\Omega\) in the secondary is:
1. \(\dfrac{1}{20}~\text{A}\)
2. zero
3. \(\dfrac{1}{10}~\text{A}\)
4. \(\dfrac{1}{5}~\text{A}\)
1. \(\dfrac{1}{20}~\text{A}\)
2. zero
3. \(\dfrac{1}{10}~\text{A}\)
4. \(\dfrac{1}{5}~\text{A}\)
Subtopic: Transformer |
74%
Level 2: 60%+
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A transformer has an efficiency of \(90\%\) when working on a \(200\) V and \(3\) kW power supply. If the current in the secondary coil is \(6\) A, the voltage across the secondary coil and the current in the primary coil, respectively, are:
1. \(300\) V, \(15\) A
2. \(450\) V, \(15\) A
3. \(450\) V, \(13.5\) A
4. \(600\) V, \(15\) A
1. \(300\) V, \(15\) A
2. \(450\) V, \(15\) A
3. \(450\) V, \(13.5\) A
4. \(600\) V, \(15\) A
Subtopic: Transformer |
73%
Level 2: 60%+
AIPMT - 2014
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