Question

In a certain material for which $\mu =4$ the magnetic field is given by,

$\overline{H}=2{\delta }_x+4{\delta }_y-8{\delta }_{z}A/m$


The corresponding magnetic energy density is ___ $\mu J/m^2$

• A. 211

Answer 1

The correct option is A 211

Magnetic energy density,

$W=\frac{1}{2}\mu |\overline{H}{|}^2$

$=\frac{1}{2}\times 4\times 4\pi \times {10}^{-7}{\left|\sqrt{2^2+4^2+8^2}\right|}^2$

$=\frac{1}{2}\times 4\times 4\pi \times {10}^{-7}[4+16+64]$

$=672\pi \times {10}^{-7}$

$W=21.1\mu J/m^2$