Question

The ratio of intensities of magnetic fields due to a short magnet in tan A and tan B position is

• A. $2:1$
• B. $1:2$
• C. $3:1$
• D. $1:3$

Answer 1

The correct option is A $2:1$

$tanA=\frac{{\mu }_0}{4\pi }\frac{2md}{{(d^2-l^2)}^2}$

$tanB=\frac{{\mu }_0}{4\pi }\frac{m}{{(d^2+l^2)}^{\frac{3}{2}}}$

incase of short bar magnet $l^2<<d^2$

$tanA=\frac{{\mu }_0}{4\pi }\frac{2m}{d^3}$

$tanB=\frac{{\mu }_0}{4\pi }\frac{m}{d^3}$

from above $\frac{tanA}{tanB}=\frac{2}{1}$