Question

A magnet of length $14cm$ and magnetic moment $M$, is broken into two parts of length $6cm$ and $8cm$ respectively. They are put at right angles to each other, with opposite poles together. The magnetic moment of the combination is

• A. $M/10$
• B. $M$
• C. $M/1.4$
• D. $2.8M$

Answer 1

The correct option is C $M/1.4$

$Solution:$

The magnetic moment of the two parts after breaking are $\frac{6}{14}M=\frac{3}{7}M$ and $\frac{8}{14}M=\frac{4}{7}M$ Their vector sum after placing at right angles $\sqrt{{\left(\frac{3}{7}M\right)}^2+{\left(\frac{4}{7}M\right)}^2}=\frac{5}{7}M=\frac{M}{1.4}$

$So,the$ $correct$ $option:C$