ElectroMagnetic InductionHard
Question
A conducting disc of radius R is placed in a uniform and constant magnetic field B parallel to the axis of the disc. With what angular speed should the disc be rotated about its axis such that no electric field develops in the disc.( the electronic charge and mass are e and m)
Options
A.
B.
C.
D.
Solution
Consider a free electron in the disc at point P distant x from centre of disc.
The magnetic force on free electron is = evB = eωxB (towards left)
Centrifugal force = mω2x. (towards right)
For net force on the electron at P to be zero
i.e., eωx B = mω2x
or ω =
There shall be no flow of free electrons radially outwards and hence no electric field shall develop within the disc
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