Q. No.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. \(4~\text k\Omega\)
1. \(30^{\circ}\)
2. \(60^{\circ}\)
3. \(45^{\circ}\)
4. \(90^{\circ}\)
1. \(\dfrac{V_0}{ \sqrt 2 R}\)
2. \(\dfrac{V_0}{ R}\)
3. \(\dfrac{ \sqrt 2 V_0}{R}\)
4. zero
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. \(R_g\)
1. \(50\) Hz
2. \(100\) Hz
3. \(200\) Hz
4. \(50\sqrt{2}\) Hz
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. |
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. | \(-{V_mI_m}\mathrm{sin}^{2}(\omega t)\) |
| 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 |
| (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)
| 1. | \(\dfrac{V_r}{3}\) | 2. | \(\dfrac{2V_r}{3}\) |
| 3. | \(\dfrac{V_r}{2}\) | 4. | \(V_r\) |
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