Question

The magnitude of magnetic induction at a point on the axis at a large distance ' \( r \) ' from the centre of a circular coil of ' \( n \) ' turns and area ' \( A \) ' carrying current ' I ' is (\( \mu_0 = \) permeability of free space)

• A. \( B_{\text{axis}} = \frac{\mu_0}{4\pi} \frac{nA}{Ir^3} \)
• B. \( B_{\text{axis}} = \frac{\mu_0}{4\pi} \frac{2nIA}{r^3} \)
• C. \( B_{\text{axis}} = \frac{\mu_0}{4\pi} \frac{2nI}{Ar^3} \)
• D. \( B_{\text{axis}} = \frac{\mu_0}{4\pi} \frac{nA}{r^3} \)

Hint:

Far from loop: - Treat it as magnetic dipole - $B_{\text{axis}} \propto \frac{1}{r^3}$

Answer 1

The Correct Option is B