2017 Moving Charges and MagnetismMagnetic Dipole Moment of Current Loop Medium Question 3 of 5 in Magnetic Dipole Moment of Current Loop

A 250-Turn rectangular coil of length 2.1 cm and width 1.25 cm carries a current of 85 $\mu A$ and subjected to a magnetic field of strength 0.85 T. Work done for rotating the coil by $180^\circ$ against the torque is

A 9.1 $\mu J$
B 4.55 $\mu J$
C 2.3 $\mu J$
D 1.15 $\mu J$

The answer is A.

Solution

Rotating from $0^\circ$ to $180^\circ$ requires $W = 2NIAB$.

$W = MB(\cos\theta_1 - \cos\theta_2)$ When it is rotated by $180^\circ$, $W = 2MB$ $W = 2(NIA)B$ $= 2\times250\times85\times10^{-6}\times[1.25\times2.1\times10^{-4}]\times85\times10^{-2}$ $= 9.1\ \mu J$

Concept magnetic-dipole-work-rotation

Magnetic Dipole Moment of Current Loop in past papers

5 questions from this chapter have appeared across 5 exam years.