A resistor of \(40~\Omega\) is connected to the secondary of a step-down transformer, with an input voltage of \(200~\text V\) and an output of \(20~\text V\) across the secondary.
The resistance as seen in the primary circuit is: (ignoring power losses)
1. \(40~\Omega\)
2. \(4~\Omega\)
3. \(0.4~\Omega\)
4. \(4~\text k\Omega\)

Subtopic:  Transformer |
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In an \(\text{AC}\) circuit, the power dissipated in a resistance is found to \(P_1\) when a source voltage of \(V_1\) is connected across it. If the same resistance is connected in series with a capacitance and the same source is connected across the combination, the power in the resistance is found to be \(P_2=\dfrac{P_1}{2}.\) The phase difference between the voltage and the current is:
1. \(30^{\circ}\)
2. \(60^{\circ}\)
3. \(45^{\circ}\)
4. \(90^{\circ}\)
Subtopic:  Different Types of AC Circuits |
From NCERT
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An alternating \(\text{emf}= V_0\sin \omega t\) is applied between the two ends \(A\) & \(B\) of the circuit shown below. The current through \(C\) has the same RMS value as that through \(R.\) The RMS value of the current flowing out at \(B\) is:
                
1. \(\dfrac{V_0}{ \sqrt 2 R}\)

2. \(\dfrac{V_0}{ R}\)

3. \(\dfrac{ \sqrt 2 V_0}{R}\)

4. zero 
Subtopic:  Different Types of AC Circuits |
From NCERT
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An alternating current generator has an internal resistance \(R_{g}\) and an internal reactance \(X_{g}\). It is used to supply power to a passive load consisting of a resistance \(R_{g}\) and a reactance \(X_{L}\). For maximum power to be delivered from the generator to the load, the value of \(X_{L}\) is equal to:
1. zero
2. \(X_g\)
3. \(-X_g\)
4. \(R_g\)

Subtopic:  Different Types of AC Circuits |
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When an AC supply of \(100\) V (rms), \(50\) Hz is applied across an inductor \(L,\) a current of \(20\) A (rms) flows; and if the same voltage is applied across a capacitor \(C,\) the same current of \(20\) A (rms) flows. A circuit is now made by connecting the inductor \(L\) and the capacitor \(C.\) The natural frequency of this \(L\)-\(C\) circuit is
1.  \(50\) Hz
2. \(100\) Hz
3. \(200\) Hz
4. \(50\sqrt{2}\) Hz
From NCERT
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Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R): 
 

Assertion (A): On the increasing frequency of a.c. through a conductor resistance of the circuit may increase.
Reason (R): Resistance of a conductor is directly proportional to the frequency of the a.c. input.


In the light of the above statements choose the correct answer from the options given below:
 

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:  Different Types of AC Circuits |
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An AC source given by \(V=V_m\sin(\omega t)\) is connected to a pure inductor \(L\) in a circuit and \(I_m\) is the peak value of the AC current. The instantaneous power supplied to the inductor is:

1. \(\dfrac{V_mI_m}{2}\mathrm{sin}(2\omega t)\) 2. \(-\dfrac{V_mI_m}{2}\mathrm{sin}(2\omega t)\)
3. \({V_mI_m}\mathrm{sin}^{2}(\omega t)\) 4. \(-{V_mI_m}\mathrm{sin}^{2}(\omega t)\)
Subtopic:  Power factor |
From NCERT
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An \(RC\) circuit is connected to a \(10\) V AC source and it is observed to supply a \(200\) mA current at a frequency of \(100\) kHz. The same resistance is now paired with an inductor \((L)\) in series and the same source supplies \(200\) mA current at a frequency of \(1\) kHz at the same operating voltage. If the circuit were made with the given \(L\text-C\text-R\) in series, the current will be a maximum when the frequency is \(f_o\). Then,
 
1. \(f_o = \dfrac{10^3 + 10^5}{2}\) Hz
2.  \(f_o > \dfrac{10^3 + 10^5}{2}\) Hz
3.  \(f_o < \dfrac{10^3 + 10^5}{2}\) Hz
4.  \(f_o = {10^3 + 10^5}\) Hz
Subtopic:  Different Types of AC Circuits |
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The line that draws the power supply to your house from the street has:
(a) zero average current
(b) \(220~\text V\)  average voltage
(c) voltage and current out of phase by \(90^\circ\)
(d) voltage and current possibly differing in phase \(\phi\) such that \(|\phi|<\dfrac \pi 2.\)
 
Choose the correct options:
1. (b), (c)
2. (a), (d)
3. (b), (d)
4. (a), (c)
Subtopic:  AC vs DC |
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The RMS voltage across the inductor is twice that across the capacitor, while the applied RMS voltage across the entire combination (i.e. \(V_{AX}\)) is \(V_r\). The RMS voltage across the capacitor is:
                        
 
1. \(\dfrac{V_r}{3}\) 2. \(\dfrac{2V_r}{3}\)
3. \(\dfrac{V_r}{2}\) 4. \(V_r\)
Subtopic:  Different Types of AC Circuits |
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