For a circular coil of radius R, magnetic field at the centre is:

B₀ = 16 μT

Find the magnetic field on its axis at a distance √3R from the centre.

Solution:

Magnetic field on axis:

B = μ₀IR² / 2(R² + x²)^3/2

At centre:

B₀ = μ₀I / 2R

Thus:

B/B₀ = R³ / (R² + x²)^3/2

Substitute x = √3R:

R² + x² = 4R²

(R² + x²)^3/2 = 8R³

B = B₀/8

= 16/8

= 2 μT

Answer: 2 μT