A circular coil of 100 turns has an effective radius of 0.05 m and carries a current of 0.1 A. How much work is required to turn it in an external magnetic field of `1.5 Wb m^-2` through `180^@` about an axis perpendicular to the magnetic field. The plane of the coil is initially perpendicular to the magnetic field.

Explanation

To solve the problem, we will calculate the work required to turn a circular coil in an external magnetic field through 180 degrees. The steps are as follows:

### Step 1: Calculate the Area of the Coil
The area \( A \) of a circular coil can be calculated using the formula:
\[ A = \pi r^2 \]
where \( r \) is the radius of the coil.
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