Alternating current cannot be measured by a DC ammeter because:
1. AC cannot pass through DC Ammeter.
2. AC changes direction.
3. Average value of current for the complete cycle is zero.
4. DC Ammeter will get damaged.

Subtopic:  AC vs DC |
 64%
From NCERT
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In an \(L\text-R\) circuit, the inductive reactance is equal to the resistance \(R\) of the circuit. An emf of \(E = E_0 \cos(\omega t)\) is applied to the circuit. The power consumed by the circuit is:
1. \(\dfrac{E^2_0}{\sqrt{2}R}\) 2. \(\dfrac{E^2_0}{4R}\)
3. \(\dfrac{E^2_0}{2R}\) 4. \(\dfrac{E^2_0}{8R}\)
Subtopic:  Power factor |
 52%
From NCERT
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A series AC circuit has a resistance of \(4~\Omega\) and an inductor of reactance \(3~\Omega\). The impedance of the circuit is \(z_1\). Now when a capacitor of reactance \(6~\Omega\) is connected in series with the above combination, the impedance becomes \(z_2\). Then \(\frac{z_1}{z_2}\) will be:
1. \(1:1\)
2. \(5:4\)
3. \(4:5\)
4. \(2:1\)

Subtopic:  Different Types of AC Circuits |
 86%
From NCERT
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An inductor \((L)\) and resistance \((R)\) are connected in series with an AC source. The phase difference between voltage \((V)\) and current \((i)\) is \(45^{\circ}.\) If the phase difference between \(V\) and \(i\) remains the same, then the capacitive reactance and impedance of the \(LCR\) circuit will be:
1. \(2R, R\sqrt{2}\)
2. \(R, R\sqrt{2}\)
3. \(R, R\)
4. \(2R, R\sqrt{3}\)

Subtopic:  Different Types of AC Circuits |
 54%
From NCERT
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What is the value of inductance \(L\) for which the current is a maximum in a series \(LCR\) circuit with \(C= 10~\mu\text{F}\) and \(\omega = 1000~\text{s}^{-1}\)?
1. \(10\) mH
2. \(100\) mH
3. \(1\) mH
4. Cannot be calculated unless \(R\) is known
Subtopic:  Different Types of AC Circuits |
 78%
From NCERT
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A \(50\) Hz AC source of \(20\) volts is connected across \(R\) and \(C\) as shown in the figure below. If the voltage across \(R\) is \(12\) volts, then the voltage across \(C\) will be:
           

1. \(8\) V
2. \(16\) V
3. \(10\) V
4. not possible to determine unless values of \(R\) and \(C\) are given
Subtopic:  Different Types of AC Circuits |
 72%
From NCERT
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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

Subtopic:  Transformer |
 73%
From NCERT
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 |
 89%
From NCERT
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 |
 69%
From NCERT
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 |
 84%
From NCERT
AIPMT - 2006
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