# Case Study Question for Class 12 Physics Chapter 7 Alternating Current

Home » CBSE Class 12 Physics » Case Study Based Questions for Class 12 Physics » Case Study Question for Class 12 Physics Chapter 7 Alternating Current

## Case Study Question for Class 12 Physics Chapter 7 Alternating Current

Question 1:

Resonant Series LCR Circuit. When the frequency of ac supply is such that the inductive reactance and capacitive reactance become equal, the impedance of the series LCR circuit is equal to the ohmic resistance in the circuit. Such a series LCR circuit is known as resonant series LCR circuit and the frequency of the ac supply is known as resonant frequency. Resonance phenomenon is exhibited by a circuit only if both L and C are present in the circuit. We cannot have resonance in a RL or RC circuit. A series LCR circuit with L = 0.12 H, C = 480 nF, R = 23 Ω is Connect to a 230 V variable frequency supply.

(i) Find the value of source for which current amplitude is maximum.
(a) 222.32 Hz
(b) 550.52 Hz
(c) 663.48 Hz
(d) 770 Hz

(ii) The value of maximum current is
(a) 14.14 A
(b) 22.52 A
(c) 50.25 A
(d) 47.41 A

(iii) The value of maximum power is
(a) 2200 W
(b) 2299.3 W
(c) 5500 W
(d) 4700 W

(iv) What is the Q-factor of the given circuit?
(a) 25 A
(b) 42.21 A
(c) 35.42 A
(d) 21.74 A

(v) At resonance which of the following physical quantity is maximum?
(a) Impedance
(b) Current
(c) Both (a) and (b)
(d) Neither (a) nor (b)