Question

The distance between the poles of a horse shoe magnet is 0.1 m and its pole strength is 0.01 amp-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)

$8 \times 10 ^ { - 7 } T$

Answer 2

Net magnetic field at mid point P,$B = B _ { N } + B _ { S }$

where $B _ { N } =$ magnetic field due to N- pole

$B _ { S } =$ magnetic field due to S- pole

$B _ { N } = B _ { S } = \frac { \mu _ { 0 } } { 4 \pi } \frac { \mathrm { m } } { r ^ { 2 } } = 10 ^ { - 7 } \times \frac { 0.01 } { \left( \frac { 0.1 } { 2 } \right) ^ { 2 } } = 4 \times 10 ^ { - 7 } T$

$\therefore B _ { \text {net } } = 8 \times 10 ^ { - 7 } \mathrm {~T}$.