A thin conducting disc of radius is free to rotate about its central vertical axis
PHYSICS · Multi-part · A Level · Physics · Fields and their consequences · Fields and their consequences
Problem
A thin conducting disc of radius 0.20m is free to rotate about its central vertical axis. The disc is placed in a uniform magnetic field of magnitude 0.50T directed vertically upward. It is set into steady rotation at 1200rpm (revolutions per minute) in the clockwise sense as seen from above.
parts:
(i) Derive an expression for the emf induced between the rim and the centre of the disc in terms of the angular speed ω, the radius r and the magnetic field B.
(ii) Using the expression obtained in part (i), calculate the numerical value of the emf for the given data.
(iii) When the disc rotates clockwise as specified, state whether the centre or the rim is at higher potential. Give a clear reason for your choice.