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Rotating disc and generators

Question: A generator designed to produce very large pulses of current, consists of a large metal disc which is accelerated to rotate at high speed. A strong, uniform magnetic field is applied perpendicular to the plane of the disc.
Each radial element of the disc can be seen as a single conductor.
Calculate the magnitude of the induced e.m.f., if the radius of the disc is 2.0 m, the speed of rotation of the disc = 3000 revolutions per minute and the magnetic flux density B = 1.8 T


The e.m.f. generated = magnetic fIux cut per second = BA per second.
Now the disc is rotating at 3000 revs per minute = 50 revs per second.

Area swept out by each radius per second = area of disc x number of revs per second
= pxR2x50 = px22 x 50 = 628.3 m2

Flux cut per second = e.m.f. generated = 628.3 x 1.8 = 1131 V

© Keith Gibbs 2011