Question

A closely wound solenoid of $750$ turns and area of cross section of $5\times {10}^{-4}{m}^2$ carries a current of $3.0$A. Its associated magnetic moment is

• A. $4.12J{T}^{-1}$
• B. $3.12J{T}^{-1}$
• C. $2.12J{T}^{-1}$
• D. $1.13J{T}^{-1}$

Answer 1

The correct option is D $1.13J{T}^{-1}$

Here, $n=750turns,A=5\times {10}^{-4}{m}^2,I=3A$
Then, magnetic moment
$m=nIA=750\times 3\times 5\times {10}^{-4}=11250\times {10}^{-4}=1.125J{T}^{-1}=1.13J{T}^{-1}$ along the axis of solenoid.