Question

The magnetic induction at a distance of 20cm on the equatorial line of a short bar magnet with a magnetic moment 60 Am${}^2$ is

• A. 7.5$\times {10}^{-3}$ T
• B. 0.75$\times {10}^{-3}$ T
• C. 0.5$\times {10}^{-3}$ T
• D. 5 $\times {10}^{-3}$ T

Answer 1

Answer: (B)

0.75$\times {10}^{-3}$ T

$d=20cm$
$m=60A{m}^2$
$B_{equi.}=\frac{{\mu }_{0}m}{4\pi d^3}$
$=\frac{4\pi \times {10}^{-7}\times 60}{4\pi \times (0.2{)}^3}$
$=7.5\times {10}^{-4}T$