Question

A closely wound solenoid of 2000 turns and area of cross-section $1.5\times {10}^4{m}^2$ carries a current of 2.0A. It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field $5\times {10}^2$ Tesla making an angle of ${30}^o$ with the axis of the solenoid. The torque on the solenoid will be

• A. $1.5\times {10}^{-3}N.m$
• B. $1.5\times {10}^{-2}N.m$
• C. $3\times {10}^{-2}N.m$
• D. $3\times {10}^{-3}N.m$

Answer 1

The correct option is B $1.5\times {10}^{-2}N.m$

$\tau =BINAsin\theta$

$=(5\times {10}^2)\left(2\right)\left(2000\right)(1.5\times {10}^4)\left(sin{30}^o\right)$

$=1.5\times {10}^{2}N.m$