Question

When a substance is kept in a magnetic field, it gets weakly repelled by the field. Which of the following represents its susceptibility?

• A. $-0.0004$
• B. $-4$
• C. $0.0004$
• D. $4$

Answer 1

The correct option is A $-0.0004$

The material gets repelled by the magnetic filed, this means that it gets oppositely magnetized to that of the external field.

$\Rightarrow \overrightarrow{I}$ and $\overrightarrow{H}$ have opposite signs.

As, $\overrightarrow{I}=\chi \overrightarrow{H}$,

$\therefore$ Magnetic susceptibility $\left(\chi \right)$ is negative for the material.

Also, $\left|I\right|<<\left|H\right|$

$\Rightarrow \left|\frac{I}{H}\right|<<1$

$\therefore \left|\chi \right|<<1$

So, $\chi$ is negative and $\left|\chi \right|<<1$.

Hence, option $\left(A\right)$ is correct.