In the given circuits \((a)\) and \((b)\) switches \({S}_1\) and \({S}_2\) are closed at \({t}=0\) and are kept closed for a long time. The variation of currents in the two circuits for \({t} \geq0\) are roughly shown by (figures are schematic and not drawn to scale):
 
1. 3.
2. 4.

 
Subtopic:  Different Types of AC Circuits |
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For the LCR circuit, shown here, the current is observed to lead the applied voltage. An additional capacitor \({C}',\) when joined with the capacitor \({C}\) present in the circuit, makes the power factor of the circuit unity. The capacitor \(C'\), must have been connected in:
 
 
1. series with \({C}\) and has a magnitude \({C\over \omega^2LC-1}\)
2. series with \({C}\) and has a magnitude \({1-\omega^2LC\over \omega^2L}\)
3. parallel with \({C}\) and has a magnitude \({1-\omega^2LC\over \omega^2L}\)
4. parallel with \({C}\) and has a magnitude \({C\over \omega^2LC-1}\)
Subtopic:  Different Types of AC Circuits |
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For an \(LCR\) circuit driven with voltage of amplitude \(V_m\) and frequency \(\omega_0=\frac{1}{\sqrt{LC}}\) the current exhibits resonance. The quality factor, \(Q\) is given by:
1. \(\frac{\omega_0 L}{R}\)
2. \(\frac{\omega_0R}{L}\)
3. \(\frac{R}{\omega_0C}\)
4. \(\frac{CR}{\omega_0}\)

Subtopic:  Different Types of AC Circuits |
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An ideal capacitor of capacitance \(0.2~ \mu \text F\) is charged to a potential difference of \(10~\text{V}.\) The charging battery is then disconnected. The capacitor is connected to an ideal inductor of self inductance \( 0.5\text{ mH.}\) The current at a time when the potential difference across the capacitor is \(5~\text{V}\) is:
1. \(0.15 ~\text{A}\)
2. \(0.17 ~\text{A}\)
3. \(0.34 ~\text{A}\)
4. \(0.25 ~\text{A}\)
Subtopic:  Different Types of AC Circuits |
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A circuit connected to an AC source of emf \(\varepsilon=\varepsilon_0\sin(100t)\) with \(t\) in seconds, gives a phase difference of \(\frac{\pi}{4}\) between the emf \(\varepsilon\) and current \(i\). Which of the following circuits will exhibit this?

1. \(RL\) circuit with \(R=1~\text{k}\Omega\) and \(L=10~\text{mH}\)
2. \(RL\) circuit with \(R=1~\text{k}\Omega\) and \(L=1~\text{mH}\)
3. \(RC\) circuit with \(R=1~\text{k}\Omega\) and \(C=1~\mu\text{F}\)
4. \(RC\) circuit with \(R=1~\text{k}\Omega\) and \(C=10~\mu\text{F}\)

Subtopic:  Different Types of AC Circuits |
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An inductance coil has a reactance of \(100~\Omega\). When an AC signal of frequency \(1000\) Hz is applied to the coil, the applied voltage leads the current by \(45^\circ\). The self-inductance of the coil is:
1. \( 1.1 \times 10^{-2} \mathrm{~H} \)
2. \(1.1 \times 10^{-1} \mathrm{~H} \)
3. \(5.5 \times 10^{-5} \mathrm{~H} \)
4. \(6.7 \times 10^{-7} \mathrm{~H} \)

Subtopic:  Different Types of AC Circuits |
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An AC circuit has \(R=100~\Omega\)\(C=2~\mu\text{F}\)\(L=80~\text{mH}\), connected in series. The quality factor of the circuit  is:
1. \(0.5\)
2. \(20\)
3. \(2\)
4. \(400\)

Subtopic:  Different Types of AC Circuits |
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A resonance circuit having inductance and resistance \(2\times 10^{-4}\) H and \(6.28~\Omega\) respectively oscillates at \(10\) MHz frequency. The value of quality factor of this resonator is: [\(\pi=3.14\)]
1. \(1000\)
2. \(2000\)
3. \(3000\)
4. \(4000\)

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A series \(LCR\) circuit is designed to resonate at an angular frequency \(\omega_0=10^5~\mathrm{rad/s}\). The circuit draws \(16\) W power from \(120\) V source at resonance. The value of resistance '\(R\)' in the circuit is:
1. \(300~\Omega\)
2. \(600~\Omega\)
3. \(900~\Omega\)
4. \(100~\Omega\)

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A transmitting station releases waves of wavelength \(960~\text{m}\). A capacitor of \(2.56~\mu F\) is used in the resonant circuit. The self-inductance of the coil necessary for resonance is:
1. \(10 \times 10^{-8} \mathrm{~H}\)
2. \(5 \times 10^{-8} \mathrm{~H}\)
3. \(10 \times 10^{-5} \mathrm{~H}\)
4. \(5 \times 10^{-4} \mathrm{~H}\)

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