A thin non conducting disc of radius R is rotating clockwise (see… - Vidyadip

MCQ

A thin non conducting disc of radius $R$ is rotating clockwise (see figure) with an angular velocity $w$ about its central axis, which is perpendicular to its plane. Both its surfaces carry $+ve$ charges of uniform surface density. Half the disc is in a region of a uniform, unidirectional magnetic field $B$ parallel to the plane of the disc, as shown. Then,

A
The net torque on the disc is zero.
✓
The net torque vector on the disc is directed leftwards.
C
The net torque vector on the disc is directed rightwards.
D
The net torque vector on the disc is parallel to $B.$

✓

Answer

Correct option: B.

The net torque vector on the disc is directed leftwards.

b

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