Question

The magnetic moment of a dipole is 2 Am${}^2$. Magnetic induction in air at a distance of 10 cm from the dipole on a line making an angle of ${60}^0$ with the axis of dipoles is :

• A. $\sqrt{7}\times {10}^{-5}T$
• B. $\sqrt{7}\times {10}^{-4}T$
• C. $\sqrt{7}/2\times {10}^{-4}T$
• D. $\sqrt{7}/2\times {10}^{-5}T$

Answer 1

The correct option is B $\sqrt{7}\times {10}^{-4}T$

Given: ${M=2Am}^2$

$r=0.1m$

$\theta ={60}^o$

We know that magnetic field is given by:

$B=\frac{{\mu }_o}{4\pi }\frac{M}{r^3}\sqrt{3co{s}^2\theta +1}$

$B={10}^{-7}\times \frac{2}{(0.1{)}^3}\sqrt{\frac{3}{4}+1}$

$⟹B=\sqrt{7}\times {10}^{-4}T$