A metal disc of radius , a =10 cm rotates with a constant angular speed of `omega = 200 rad//s` about its axis.
The potential difference between the centre and the rim of the disc under a uniform magnetic field, B= 5 mT directed perpendicular to the disc, is

Options

A. 2 mV
B. 5 mV
C. 10 mV
D. 15 mV

Answer

B

Explanation

Key Idea induced emf due to a rotating metallic disc in uniform magnetic filed B is given by expression,
`e= 1/2 B omega a^2`
where `omega `= angular speed and a = radius of the disc given, radius of metallic disc a = 10 cm , angular speed of metallic disc `omega = 200 rad//sec` and magnetic field B = 5 mT
now putting the values in above expression,
`e =1/2 B omega a^2 = 1/2 xx 200 xx 5 xx 10^(-3) xx(10xx10^(-2))^2`
`rArr e = 5 mV`