Question

A $100$ turn closely wound circular coil of radius $ 10\,cm $ carries a current of $ 3.2\,A $ . The magnetic moment of the coil is, approximately

• A. $ 5\,A\,m^{2} $
• B. $ 10\,A\,m^{2} $
• C. $ 20\,A\,m^{2} $
• D. $ 40\,A\,m^{2} $

Answer 1

Answer: (B)

Magnetic moment,
$ M=niA $
$ M=100\times 3.2\times (\pi r_{1}^{2}) $
$ =100\times 3.2\times \frac{22}{7}\times \frac{10}{100}\times \frac{10}{100} $
$ =10.048\,A-m^{2} $