When induced `emf` in inductor coil is `50%` of its maximum value then stored energy in inductor coil in the given circuit at that instant will be:-

Options

A. `2.5 mJ`
B. `5 mJ`
C. 15 mJ
D. 20 mJ

Answer

A

Explanation

If the maximum value of induced EMF is V then 50% of induced EMF is `(V)/(2).` Also, at this moment voltage across resistor will be `(V)/(2).`
`E =(1)/(2) Li ^(2)`
`E = (1)/(2) L (((V)/(2))/(R ))^(2)`
`E = (1)/(2) ( 5 xx 10 ^(-3)) ((2)/(2 1)) ^(2)`
`E = 2. 5 mJ`