Magnetic moment of a thin bar magnet is 'M.' If it is bent into a semicircular form, its new magnetic moment will be _________.
Fill in the blank with the correct answer from the options given below.
Answer & explanation
Correct answer: option 4
Initial magnetic moment is $ M = mL$
Final magnetic moment is $ M' = m\times 2R $
$ L = \pi R \Rightarrow M' = m\times \frac{2L}{\pi} = \frac{2M}{\pi}$
The correct answer is Option (4) → $2 M / \pi$