Question

A circular coil of $300$ turns and diameter $14\, cm$ carries a current of $15 \,A$. The magnitude of magnetic moment associated with the loop is

• A. $51.7\, J\, T^{-1}$
• B. $69.2\, J\, T^{-1}$
• C. $38.6\, J\, T^{-1}$
• D. $19.5\, J\, T^{-1}$

Answer 1

Answer: (B)

$69.2\, J\, T^{-1}$

Answer 2

Here, $N = 300$, $I = 15 \,A$, $r = 7 \,cm = 7 \times 10^{-2} \,m$ $\therefore\quad M = NIA = NI \times \pi r^{2}$ $= 300 \times 15 \times 3.14 \times \left(7 \times 10^{-2}\right)^{2} = 69.2\, J \,T^{-1}$