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. `50 mu F`
B. `25 mu F`
C. `100 mu F`
D. `12.5 mu F`

Answer

B

Explanation

Energy produced is stored in capacitor
`:." "(1)/(2)"CV"^(2)=(1)/(2)LI^(2)`
or `" "C(400)^(2)=1xx(2)^(2)`
or `" "C(400)^(2)=4`
`:." "C=(4)/((400)^(2))=(1)/(4xx10^(4))`
`=25xx10^(-6)F=25muF`