Q. No.
In an L-R circuit, the inductive reactance is equal to the resistance R of the circuit. An emf of E = E0cos(ωt) is applied to the circuit. The power consumed by the circuit is:
1.
2.
3.
4.
A series AC circuit has a resistance of 4 and an inductor of reactance 3 . The impedance of the circuit is z1. Now when a capacitor of reactance 6 is connected in series with the above combination, the impedance becomes will be:
1. 1 : 1
2. 5 : 4
3. 4 : 5
4. 2 : 1
An inductor (L) and resistance (R) are connected in series with an AC source. The phase difference between voltage (V) and current (i) is . If the phase difference between V and i remains the same, then the capacitive reactance and impedance of the L-C-R circuit will be:
1. 2R, R
2. R, R
3. R, R
4. 2R, R
Alternating current cannot be measured by a D.C. ammeter because:
| 1. | A.C. cannot pass through D.C. Ammeter |
| 2. | A. C. changes direction |
| 3. | Average value of current for the complete cycle is zero |
| 4. | D.C. Ammeter will get damaged |
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
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 |
How much power is dissipated in an \(\mathrm{L-C-R}\) series circuit connected to an \(\mathrm{AC}\) source of emf \(\mathrm E\)?
| 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. | \(\frac{\varepsilon^{2}R}{\sqrt{R^{2}+\left(L \omega-\frac{1}{C \omega}\right)^{2}}}\) |
A coil of inductive reactance of 31 Ω has a resistance of 8 Ω. It is placed in series with a condenser of capacitive reactance 25 Ω. The combination is connected to an a.c. source of 110 V. The power factor of the circuit is:
1. 0.56
2. 0.64
3. 0.80
4. 0.33
1. 3.6 A
2. 2.8 A
3. 2.5 A
4. 5.0 A
An alternating voltage source is connected to a series R-C circuit. Consider two situations:
| 1. | When the capacitor is air-filled. |
| 2. | When the capacitor is mica filled. |
If the current through the resistor is I and the voltage across the capacitor is V, then:
1. \(V_a < V_b\)
2. \(V_a > V_b\)
3. \(i_a > i_b\)
4. \(V_a = V_b\)
© 2024 GoodEd Technologies Pvt. Ltd.