Question

A circular coil of 250 turns and diameter 18 cm carries a current of 12A. What is the magnitude of magnetic moment associated with the coil?

Answer 1

M = N I A where A =π r² 

∴ M = NI π r2
∴ M = 250 x 12 x 3.14 x 81 x10^-4
∴ M = 76.30 A-m²