Question

Assertion If a bar magnet is split parallel to its length in $n$ parts, then magnetic moment of each part becomes $1 / n$ times.
Reason In this case the pole strength of each part remains as before but length becomes $1 / n$ times.

• A. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion
• B. If both Assertion and Reason are true but Reason is not correct explanation of the Assertion
• C. If Assertion is true but Reason is false
• D. If Assertion is false but the Reason is true

Answer 1

Answer: (A)

The magnet is cut parallel to its length of its each part will be of the same length as previous but the pole strength of each part,
$=\frac{1}{n} \times$ initial pole strength
$\therefore m'=\frac{m}{n}$
Therefore, the magnetic moment
$=m' \times l'=\frac{m}{n} \times l=\frac{1}{n}(m l)=\frac{M}{n}$
Hence, the magnetic moment of each part becomes $1 / n$ times.