Question

A coil of resistance $10\,\Omega$ and inductance $5\, H$ is connected to a $100\, V$ battery. Then the energy stored in the coil is

• A. $250\,J$
• B. $250\,erg$
• C. $125\,J$
• D. $125\,erg$

Answer 1

Answer: (A)

$250\,J$

Answer 2

Final current, $I=\frac{E}{R}$
$I=10\,A$
Energy stored in the magnetic field
$U=\frac{1}{2}\,Li$
$\frac{1}{2}\times5\times\left(10\right)^{2}=250\,J$