Question

A circular coil of $200$ turns and radius $10cm$ is placed in a uniform magnetic field of $0.5T$ , normal to the plane of the coil. If the current in in the coil is $3.0A$ , calculate the
(a) total torque on the coil
(b) total force on the coil
(c) average force on each electron in the coil, due to the magnetic field.

Answer 1

(a)$As\overrightarrow{B}is\parallel todipolemomemt\overrightarrow{M}$

$\therefore \tau =BMsin{0}^o=0$

(b)As the force on different parts of the coil appears in pairs, equal in

magnitude, and opposite in direction, net force on coil is zero.

(c)$F=Be{v}_d$

$F=Be{v}_d=Be\frac{1}{neA}=\frac{0.5\times 3}{{10}^{29}\times {10}^{-5}}=1.5\times {10}^{-24}N$