CBSE Class 12 Physics Alternating Current Subjective Problems

CBSE Class 12 Physics Alternating Current Subjective Problems. Please refer to the examination notes which you can use for preparing and revising for exams. These notes will help you to revise the concepts quickly and get good marks.

1. Find the value of inductance which should be connected in series with a capacitance of 0.5 μF, a resistance of 10 ohms and an A.C. source of 50 caps so that the power factor of the circuit is unity.

2. A coil of resistance 60 ohms and inductance 3 henry is connected in series with a condenser of 4 μF and an a.c. supply of 200 volts and 50 c/s. Calculate
(a) the impedance of the circuit
(b) phase difference between current and voltage
(c) p.d. across the inductance coil, and
(d) p.d. across the capacitor

3. A 200 km long telegraph wire has a capacity of 0.014 μ F/km. If it carries an alternating current of frequency 5 KHz, find the value of the inductance which should be connected in series so that the impedance is minimum.

4. A circuit draws a power of 550 watt from a source of 220 Volt, 50 Hertz. The power factor of the circuit is 0.8 and the current lags in phase behind the potential difference. If the power factor of the circuit is to be increased to 1.0, find the value of capacitance which should be connected.

5. Prove that in a series LCR circuit, the frequencies f1 and f2 at which the current amplitude falls to 1/√2 of the current at resonance are separated by an interval equal to (R/2πL)

6. A series circuit consists of a resistance, inductance and capacitance. The applied voltage and the current at any time t are respectively given by E=141.4 cos (3000t–10) and I=5 cos(3000t–550). If the inductance is 0.01 henry, find the values of the resistance and capacitance.

7. A 100 μ F capacitor in series with a 40Ω resistance is connected to a 110 V, 60 Hz supply. Find the maximum current in the circuit. Also find the time lag between the maximum current and maximum voltage.

8. A 20 volts 5 watt lamp is used on a.c. mains of 220 volts and 50 Hz. Find
(a) the values of
(i) capacitor and
(ii) inductor to be put in series with the lamp to run it.
(b) the value of pure resistance which should be connected in series with the lamp to run it.

9. A choke coil is required to operate an arc lamp at 160 V r.m.s. and 50 Hz. The arc lamp has an effective resistance of 5Ω when running at 10 A r.m.s. Find the inductance of the choke coil. If the same arc lamp is operated on 160 V d.c., find the additional resistance required and power loss if d.c. is used.

Please click on below link to download pdf file for CBSE Class 12 Physics Alternating Current Subjective Problems