Question

A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic substance. The whole system is placed in a uniform magnetic field $B$. Then the field inside the paramagnetic substance is:

• A. Much large than $\begin{array}{l}\left|\overrightarrow{B}\right|\end{array}$and parallel to $\begin{array}{l}\overrightarrow{B}\end{array}$
• B. ZERO
• C. $\overrightarrow{B}$
• D. Much large than $\begin{array}{l}\left|\overrightarrow{B}\right|\end{array}$and opposite to $\begin{array}{l}\overrightarrow{B}\end{array}$

Answer 1

The correct option is B

ZERO

Step 1. Given Data:

A perfectly diamagnetic sphere has a small spherical cavity at its center.

This setup is placed in a Uniform Magnetic Field $B$.

Step 2. The Field inside the paramagnetic substance is:

1. A perfect diamagnetic substance expels the magnetic field completely, as shown in the figure.
2. Thus inside the cavity, there will be no Magnetic Field.
3. Since the Paramagnetic Substance is kept inside the cavity then it will experience no force.
4. Therefore, Magnetic Field inside the Paramagnetic Substance is zero.

Hence, the correct option is (B).