Question

A closely wound solenoid of $1000$ turns and area of cross section $1.4 \times 10^{-4}\, m^2$ carrying a current of $3 \,A$ is suspended through its centre allowing it to turn in a horizontal plane. The magnetic moment associated with this solenoid is

• A. $0.22\,J \,T^{-1}$
• B. $0.32\,J \,T^{-1}$
• C. $0.42\,J \,T^{-1}$
• D. $0.52\,J \,T^{-1}$

Answer 1

Answer: (C)

Here, $n = 1000$,
$A = 1.4 \times 10^{-4} \,m^{2}$, $I = 3\, A$
$m = nlA = 1000 \times 3 \times 1.4 \times 10^{-4} $
$= 0.42 \,J \,T^{-1}$