Question

The distance between the poles of a horse shoe magnet is $0.1m$ and its pole strength is $0.01amp-m$. The induction of magnetic field at a point midway between the poles will be

• A. $2\times 10^{-5}T$
• B. $4\times 10^{-6}T$
• C. $8\times 10^{-7}T$
• D. Zero

Answer 1

Answer: (C)

Net magnetic field at mid-point $P,B=B_N+B_S$
where $B_N=$ magnetic field due to $N$-pole
$B_S=$ Magnétic field due to $S$-pole
$B_N=B_S=\frac{{\mu }_0}{4\pi }\frac{m}{r^2}$

$=10^{-7}\times \frac{0.01}{{\left(\frac{0.1}{2}\right)}^2}=4\times 10^{-7}T$
$\therefore B_{\text{net }}=8\times 10^{-7}T$