Question

A 200 turn closely wound circular coil of radius 15 cm carries a current of 4 A. The magnetic moment of this coil is:

• A. $36.5A{m}^2$
• B. $56.5A{m}^2$
• C. $66.5A{m}^2$
• D. $108A{m}^2$

Answer 1

The correct option is B $56.5A{m}^2$

The magnetic moment is given by
$|\overline{m}|=NIA=NI\pi r^2$

$=200\times 4\times 3.14\times (15\times {10}^{-2}{)}^2$

$=200\times 4\times 3.14\times 15\times 15\times {10}^{-4}$

$=56.5A{m}^2$