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Q. No.In AC (alternating current) generator, a coil of wire rotates in a magnetic field.
Which of the following would change the potential difference measured by the voltmeter in the system above?
(a)
use more turns of wire in the coil.
(b)
use thicker wire.
(c)
change the speed of rotation.
Choose the correct option from the given ones:
1.
(c) only
2.
(a), (b) and (c)
3.
(a) and (b) only
4.
(a) and (c) only
Subtopic: AC Generator |
55%
Level 3: 35%-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 |
74%
Level 2: 60%+
AIPMT - 2014
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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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How much power is dissipated in an \(LCR\) series circuit connected to an \(\text{AC}\) source of emf \( E\)?
| 1. | \(\frac{\varepsilon^{2} R}{\left[R^{2}+\left(L \omega-\frac{1}{C \omega}\right)^{2}\right]}\) | 2. | \(\frac{\varepsilon^{2} \sqrt{R^{2}+\left(L \omega-\frac{1}{C \omega}\right)^{2}}}{R}\) |
| 3. | \(\frac{\varepsilon^{2}\left[R^{2}+\left(L \omega-\frac{1}{C \omega}\right)^{2}\right]}{R}\) | 4. | \(\frac{\varepsilon^{2}R}{\sqrt{R^{2}+\left(L \omega-\frac{1}{C \omega}\right)^{2}}}\) |
Subtopic: Power factor |
71%
Level 2: 60%+
AIPMT - 2009
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A coil of inductive reactance of \(31~\Omega\) has a resistance of \(8~\Omega\). It is placed in series with a condenser of capacitive reactance \(25~\Omega\). The combination is connected to an AC source of \(110\) V. The power factor of the circuit is:
1. \(0.56\)
2. \(0.64\)
3. \(0.80\)
4. \(0.33\)
Subtopic: Power factor |
87%
Level 1: 80%+
AIPMT - 2006
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A \(220\) V input is supplied to a transformer. The output circuit draws a current of \(2.0\) A at \(440\) V. What is the current drawn by the primary windings of the transformer if the efficiency of the transformer is \(80\%\)?
1. \(3.6\) A
2. \(2.8\) A
3. \(2.5\) A
4. \(5.0\) A
1. \(3.6\) A
2. \(2.8\) A
3. \(2.5\) A
4. \(5.0\) A
Subtopic: Transformer |
77%
Level 2: 60%+
AIPMT - 2010
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An alternating voltage source is connected to a series \(RC\) circuit. Consider two situations:
| 1. | When the capacitor is air-filled. |
| 2. | When the capacitor is mica filled. |
If the current through the resistor is \(I\) and the voltage across the capacitor is \(V\), then:
1. \(V_a < V_b\)
2. \(V_a > V_b\)
3. \(i_a > i_b\)
4. \(V_a = V_b\)
Subtopic: Different Types of AC Circuits |
67%
Level 2: 60%+
NEET - 2015
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A resistance \(R\) draws power \(P\) when connected to an AC source. If an inductance is now placed in series with the resistance, such that the impedance of the circuit becomes \(Z\) the power drawn will be:
\(1 .\) \(P \left(\frac{R}{Z}\right)^{2}\)
\(2 .\) \(P \sqrt{\frac{R}{Z}}\)
\(3 .\) \(P \left(\frac{R}{Z}\right)\)
\(4 .\) \(P\)
\(1 .\) \(P \left(\frac{R}{Z}\right)^{2}\)
\(2 .\) \(P \sqrt{\frac{R}{Z}}\)
\(3 .\) \(P \left(\frac{R}{Z}\right)\)
\(4 .\) \(P\)
Subtopic: Power factor |
60%
Level 2: 60%+
NEET - 2015
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The diagram shows a capacitor \(C\) and a resistor \(R\) connected in series to an AC source. \(V_1\) and \(V_2\) are voltmeters and \(A\) is an ammeter.
Which of these statements is/are correct?
| I. | Readings in \(A\) and \(V_2\) are always in phase |
| II. | Reading in \(V_1\) is ahead in phase with reading in \(V_2\) |
| III. | Readings in \(A\) and \(V_1\) are always in phase |
| 1. | I only | 2. | II only |
| 3. | I and II only | 4. | II and III only |
Subtopic: Different Types of AC Circuits |
64%
Level 2: 60%+
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The figure shows the variation of \(R\), \(X_L\), and \(X_C\) with frequency \(f\) in a series of \(L\), \(C\), and \(R\) circuits. For which frequency point is the circuit inductive?
| 1. | \(A\) | 2. | \(B\) |
| 3. | \(C\) | 4. | All points |
Subtopic: Different Types of AC Circuits |
57%
Level 3: 35%-60%
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