A metal disk of radius R, thickness d, and conductivity lies in the x-y plane and is cantered at the origin. There is a

A metal disk of radius R, thickness d, and conductivity σ lies in the x-y plane and is cantered at the origin. 

There is a time-dependent, uniform magnetic field permeating the region.

(a) Determine the induced current density in the disk. 

(b) Determine the power dissipated by Joule heating in the disk.