Question

Assertion $\left(A\right)$ : The poles of a magnet cannot be separated by breaking into two pieces.

Reason $\left(R\right)$ :The magnetic moment will be reduced to half when a magnet is broken into two equal pieces.

• A. Both $\left(A\right)$ and $\left(R\right)$ are true, $\left(R\right)$ is the correct explanation of $\left(A\right)$
• B. Both $\left(A\right)$ and $\left(R\right)$ are true, $\left(R\right)$ is not the correct explanation of $\left(A\right)$
• C. $\left(A\right)$ is true but $\left(R\right)$ is false.
• D. $\left(A\right)$ is false but $\left(R\right)$ is true.

Answer 1

The correct option is B Both $\left(A\right)$ and $\left(R\right)$ are true, $\left(R\right)$ is not the correct explanation of $\left(A\right)$

As we know, every atom of a magnet acts as a dipole. So poles cannot be separated.

As we know, magnetic moment is,

$M=m\left(2l\right)$

Where, $m=\text{Pole strength}\left(2l\right)=\text{Length of the magnet}$

When a magnet is cut into equal pieces perpendicular to its axis, its pole strength remains the same but its length becomes half the initial length i.e., $m^{{}^{\prime }}=m;(2l{)}^{{}^{\prime }}=\frac{2l}{2}$

Thus new magnetic moment of each piece is,

$M^{{}^{\prime }}=m^{{}^{\prime }}(2l{)}^{{}^{\prime }}=ml$

Hence, the new magnetic moment of each piece is, half of its initial magnetic moment.

<!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Hence, $\left(B\right)$ is the correct answer.