Question

$A$ $200$ turn closely wound circular coil of radius $15cm$ carries a current of $4A$. 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

Answer: (B)

The magnetic moment is given by
$\left|\vec{m}\right|=NIA=NI\pi r^2=200\times 4\times 3.14\times {\left(15\times 10^{-2}\right)}^2$
$=200\times 4\times 3.14\times 15\times 15\times 10^{-4}$
$=56.5A{m}^2$