A coil of inductance 2H having negligible resistance is connected to a source of supply whose voltage is given by V = 3t volt. (where t is in second). If the voltage is applied when t = 0, then the energy stored in the coil after 4s is J.

Answer

144

Explanation

`L (di)/(dt) =e`
`=3t`
`L int di = 3 int idt`
`Li = (3t^2)/2`
`i=(3t^2)/(2L)`
Energy `E=1/2 Li^2`
`=1/2L((3t^2)/(2L))^2`
`=1/2 xx(9t^4)/(4L)`
`=9/8xx((4)^4)/(2)=144J`