Question

A horizontal overhead powerline is at height of $4m$ from the ground and carries a current of $100\,A$ from east to west. The magnetic field directly below it on the ground is $\left(\mu_{0} = 4\pi \times10^{-7} Tm A^{-1}\right) $

• A. $2.5 \times10^{-7} T $ southward
• B. $5 \times10^{-6} T $ northward
• C. $5 \times10^{-6} T $ southward
• D. $2.5 \times10^{-7} T $ northward

Answer 1

Answer: (C)

The magnetic field $B = \frac{\mu_{0}}{4\pi} \frac{2I}{r}$
$ = 10^{-7} \times\frac{2\times100}{4} $
$= 5 \times10^{-6} T$
According to right hand palm rule, the magnetic field is directed towards south.