Assertion (A): | If the terminals of the primary of a transformer are connected across a battery then no emf is induced across the secondary in a steady state. |
Reason (R): | The battery provides a steady current, so there is no change in flux linked with the secondary. |
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. |
Column-I | Column-II | ||
(A) | \(I=I_0\sin\omega t\) | (P) | only inductor circuit |
(B) | \(I=-I_0\cos\omega t\) | (Q) | may be \(C\text{-}R\) circuit |
(C) | \(I=I_0 \sin \left(\omega t+\frac{\pi}{4}\right)\) | (R) | may be \(L\text{-}R\) circuit |
(D) | \(I=I_0 \sin \left(\omega t-\frac{\pi}{4}\right)\) | (S) | only resistance circuit |
1. | A → S, B → Q, C → P, D → R |
2. | A → P, B → S, C → R, D → Q |
3. | A → S, B → P, C → Q, D → R |
4. | A → S, B → P, C → R, D → Q |
Assertion (A): | Large-scale transmission and distribution of electric energy over long distances are done by stepping the voltage up by a transformer. |
Reason (R): | This cuts down the loss of energy due to eddy currents. |
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. |
Assertion (A): | If the frequency of the applied AC is doubled, then the power factor of a series R-L circuit decreases. |
Reason (R): | \(\cos \theta=\frac{2 \mathrm{R}}{\sqrt{\mathrm{R}^{2}+\omega^{2} \mathrm{~L}^{2}}}.\) | Power factor of series R-L circuit is given by
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. |
1. | voltage across the capacitor lags behind the current. |
2. | voltage across the inductor leads the current. |
3. | voltage across \(\text{R}\) is in phase with the current. |
4. | all of the above. |
A series LCR circuit containing \(5.0~\text{H}\) inductor, \(80~\mu \text{F}\) capacitor and \(40~\Omega\) resistor is connected to \(230~\text{V}\) variable frequency AC source. The angular frequencies of the source at which power transferred to the circuit is half the power at the resonant angular frequency are likely to be:
1. | \(46~\text{rad/s}~\text{and}~54~\text{rad/s}\) |
2. | \(42~\text{rad/s}~\text{and}~58~\text{rad/s}\) |
3. | \(25~\text{rad/s}~\text{and}~75~\text{rad/s}\) |
4. | \(50~\text{rad/s}~\text{and}~25~\text{rad/s}\) |
A lamp is connected in series with a capacitor. AC and DC sources are connected to the circuit one by one, then mark the correct statement/s.
1. | when the DC source is connected to the capacitor, the lamp will not glow in a steady-state condition. |
2. | when the AC source is connected to the capacitor and the capacitance of the capacitor is reduced, the lamp will glow less brightly. |
3. | when the DC source is connected to the capacitor and the capacitance of the capacitor is reduced, the lamp will glow less brightly. |
4. | both (1) and (2). |
Turn ratio of a step-up transformer is \(1: 25\). If current in load coil is \(2~\text{A}\), then the current in primary coil will be:
1. | \(25~\text{A}\) | 2. | \(50~\text{A}\) |
3. | \(0.25~\text{A}\) | 4. | \(0.5~\text{A}\) |
A coil has a resistance of \(30~ \mathrm{ohm}\) and inductive reactance of \(20 ~\mathrm{ohm}\) at a \(50~\mathrm{ Hz}\) frequency. If an \(\mathrm{ac}\) source of \(200 ~\mathrm{volts,}\) \(100~\mathrm{ Hz}\) is connected across the coil, the current in the coil will be:
1. | \(2.0~\mathrm{ A}\) | 2. | \(4.0~\mathrm{ A}\) |
3. | \(8.0~\mathrm{ A}\) | 4. | \(20/\sqrt{13}~\mathrm{A}\) |