All Problems Electromagnetic Induction. Maxwells Equations
Problem 3.290
A metal disc of radius \(a=25 \mathrm{~cm}\) rotates with a constant angular velocity \(\omega=130 \mathrm{rad} / \mathrm{s}\) about its axis. Find the potential difference between the centre and the rim of the disc if (a) the external magnetic field is absent; (b) the external uniform magnetic field of induction \(B=5.0 \mathrm{mT}\) is directed perpendicular to the disc.
(a) \(\Delta \varphi=1 / 2 \omega^{2} a^{2} m / e=3.0\) nV; (b) \(\Delta \varphi \approx 1 / 2 \omega B a^{2}= 20 mV\)