Question

The distance between the poles of a horse shoe magnet is 0.1 m and its pole strength is 0.01 A-m. The induction of magnetic field at a point mid way between the poles will be :

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

Answer 1

The correct option is D $8\times {10}^{-7}T$

Net magnetic field at mid point O
$B_{net}=B_N+B_S$
where, $B_N=$ magnitude of magnetic field due to N-pole and $B_S=$ magnitude of magnetic field due to S-pole.
But, $B_N=B_S=\frac{{\mu }_0}{4\pi }\frac{m}{r^2}$
$=\frac{4\pi \times {10}^{-7}\times 0.01}{4\pi \times (\frac{0.1}{2}{)}^2}=4\times {10}^{-7}T$
$\therefore B_{net}=8\times {10}^{-7}T$