Question

A circuit has a self-inductance of 1 H and carries a current of 2A. To prevent sparking, when the circuit is switched off, a capacitor which can withstand 400 V is used. The least capacitance of the capacitor connected across the switch must be equal to?

• A. 50 μF
• B. 25 μF
• C. 100 μF
• D. 12.5 μF

Hint:

The least capacitance can be calculated by equating the energy stored in the inductor to that in the capacitor.

Answer 1

The Correct Option is B

To prevent sparking, the capacitor needs to absorb the energy stored in the inductor when the circuit is switched off. The capacitance needed can be calculated using the energy balance between the inductor and the capacitor.