Question

If the current in an inductor coil changing from $+8A$ to $+2A$ in $0.06s$ induces $12V$ across it, the final energy stored in the coil is

• A. 240 mJ
• B. 60 mJ
• C. 360 mJ
• D. 960 mJ

Answer 1

The correct option is A 240 mJ

$ϵ=Ldi/dt,E=\frac{1}{2}L{i}^2$ $L=\frac{ϵ}{\left(\frac{di}{dt}\right)}=\frac{12}{\left(\frac{6}{0.06}\right)}=\frac{12\times 0.06}{6}=0.12H$ Energy = $\frac{1}{2}L{i}^2=\frac{1}{\text{/}2}\left(0.12\right)\text{/}2.2=0.24=240mJ$