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

Options

A. 75 `mu`F.
B. 50 `mu`F.
C. 25 `mu`F.
D. 12.5 `mu`F.

Answer

C

Explanation

(c ) To prevent sparking capacitance should be such that energy stored in capacitor is equal to the energy stored in inductor.
`implies (1)/(2)CV^(2)= (1)/(2) LI^(2)`
`implies C(400)^(2)= 1xx(2)^(2)`
`implies C= 25 muF `
Hence option C is correct.