Question

A short magnet when placed at a distance of $15cm$ in $Tan$ $A$ position produces ${60}^o$ deflection. If the magnet is cut into 3 equal parts and one of them is kept at the same distance in $Tan$ $A$ position, the deflection is:

• A. ${20}^o$
• B. ${30}^o$
• C. ${45}^o$
• D. ${60}^o$

Answer 1

Answer: (B)

${30}^o$

At $15cm,B_H\tan \theta =\frac{{\mu }_0}{4\pi }.\frac{2M}{d^3}⟹\frac{\tan {\theta }_2}{\tan {\theta }_1}=\frac{M_2}{M_1}$

$⟹\frac{\tan {\theta }_2}{\tan {\theta }_1}=\frac{M}{3M}⟹\tan {\theta }_2=\frac{1}{\sqrt{3}}⟹{\theta }_2=30°$