An inductor coil stores 32 J of magnetic field energy and dissiopates energy as heat at the rate of 320 W when a current of 4 A is passed through it. Find the time constant of the circuit when this coil is joined across on ideal battery.

Options

A. `0.1sec`
B. `0.2sec`
C. `0.3sec`
D. `0.4sec`

Answer

B

Explanation

`(1)/(2)Li^(2)=32 implies (1)/(2)Lxx(4)^(2)=32`
`L=4H`
`i^(2)R=320 implies (4)^(2)R=320`
`R=20QOmega`
`tau=(L)/(R)=(4)/(20)=0.2sec`