Question

Two points A and B are at equal distance from the centre of a small bar magnet. Point A is on the axial line and point B is on the line bisecting the magnet at right angles. If the distance of the points from the magnet is much greater than the length of the magnet, the ratio of the fields at point A and B is :

• A. $2:1$
• B. $1:2$
• C. $1:1$
• D. $4:1$

Answer 1

The correct option is A $2:1$

$B_1=\frac{2{\mu }_{o}M}{4\pi d^3}$ (On axial line)
$B_1=\frac{{\mu }_{o}M}{4\pi d^3}$ ( for equatorial line)
$A=\frac{2{\mu }_{o}M}{4\pi d^3}$
$B=\frac{-{\mu }_{o}M}{4\pi d^3}$

$A:B=2:1$

$M:$ Dipole Moment
$d:$ Distance from the center of the magnet