# Physics Class 12 NCERT Solutions: Chapter 7 Alternating Current Part 6 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Q: 15. A capacitor in series with a resistance is connected to a supply.

(A) What is the maximum current in the circuit?

(B) What is the time lag between the current maximum and the voltage maximum?

Capacitance of the capacitor,

Resistance of the resistor,

Supply voltage,

(a) Frequency of oscillations,

Angular frequency,

For a circuit, we have the relation for impedance as:

Peak voltage,

Maximum current is given as:

(B) In a capacitor circuit, the voltage lags behind the current by a phase angle of . This angle is given by the relation:

Hence, the time lag between maximum current and maximum voltage is 1.55 ms.

Q: 16. Obtain the answers to (a) and (b) in Exercise 15 if the circuit is connected to a supply? Hence, explain the statement that a capacitor is a conductor at very high frequencies. Compare this behavior with that of a capacitor in a circuit after the steady state.

Capacitance of the capacitor,

Resistance of the resistor,

Supply voltage,

Frequency of the supply,

Angular Frequency,

Peak voltage,

Maximum current,

For an circuit, the voltage lags behind the current by a phase angle of given as:

Hence, tends to become zero at high frequencies. At a high frequency, capacitor acts as a conductor.

In a dc circuit, after the steady state is achieved . Hence, capacitor amounts to an open circuit.

Developed by: