Question

Consider a small cube of volume 1 mm3 at the centre of a circular loop of radius 10 cm carrying a current of 4 A. Find the magnetic energy stored inside the cube.

Answer 1

Magnetic Energy Stored is $8\pi \times 10^{-14} J$

Explanation:

Energy density = $B^2/2\mu_0$

Total energy stored

= $\frac {B^2V}{2\mu_0} = \frac {(\mu_0 i/2r)^2}{2\mu_0} V$

= $\frac {\mu_0 i^2}{4r^2 \times 2} V$

= $\frac {4\pi \times10^-^7 \times 4^2 \times 1 \times 10^-^9}{4 \times(10^-^1)^2 \times 2}$

= $8\pi \times 10^{-14}$ J