A conducting disc of radius r spins about its axis with an angular velocity ω. There is a uniform magnetic field of magnitude B perpendicular to the plane of the disc. C is the centre of the ring.
(a) No emf is induced in the disc.
(b) The potential difference between C and the rim is 1/2 Br2ω.
(c) C is at a higher potential than the rim.
(d) Current flows between C and the rim.
