A hollow cylinder made of material of resistivity `rho` has length a and wall thickness `d(l gt gt a gt gt d)`. A current I flows through the cylinder in tangential direction and is uniformly distributed along its length.
(a) Find the emf developed along the circumference of the cylinder if the current changes at a rate `(dl)/(dt) = beta`
(b) Assume that no external source is present and the current at time t = 0 is `I_(0)`. The current decays with time. Write I as a function of time.

Answer

(a) `(mu_(0)pia^(2)beta)/(l)` (b) `I = I_(0)e^(-(2rhot)/(mu_(0)ad))`