Question

A thin metallic disc is rotating with constant angular velocity about a vertical axis that is perpendicular to its plane and passes through its centre. The rotation causes the free electrons in the disc to redistribute. Assume that, there is no external electric or magnetic field. Then,

• A. a point on the rim of the disc is at a higher potential than its centre
• B. a point on the rim of the disc is at a lower potential than its centre
• C. a point on the rim of the disc is at the same potential as its centre
• D. the potential in the material has an extremum between centre and the rim

Answer 1

Answer: (B)

Centrifugal action causes electrons to accumulate around rim of disc.

So, rim of disc is at a negative potential with respect to centre of disc. $So,$ points of rim are at lower potential than its centre.