Question

Magnetic field due to a short bar magnet on its equatorial line at a certain distance is $B$. Find out its value at the same distance on the axial line?

• A. $2B$
• B. $\frac{B}{2}$
• C. $3B$
• D. $\frac{B}{3}$

Answer 1

Answer: (A)

$2B$

Magnetic field of induction on the axial line is,
$B=\frac{{\mu }_0}{4\pi }\frac{2M}{d^3}N{A}^{-2}{m}^{-2}$
Magnetic field of induction on the equator is,
$B=\frac{{\mu }_0}{4\pi }\frac{M}{d^3}N{A}^{-2}{m}^{-2}$
Ratio of magnetic field of induction on axial line to equitorial line is
$=2:1$
Therefore $B$ on equator implies $2B$ on axial line, correct answer is option A