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,
- AThe net torque on the disc is zero.
- BThe net torque vector on the disc is directed leftwards.
- CThe net torque vector on the disc is directed rightwards.
- DThe net torque vector on the disc is parallel to $B.$