Problem 5.6 (a) A phonograph record carries a uniform density of "static electricity" o. If it rotates at angular velocity w, what is the surface current density K at a distance r from the center? (b) A uniformly charged solid sphere, of radius R and total charge Q, is centered at the origin and spinning at a constant angular velocity w about the z axis. Find the current density J at any point (r, 0, p) within the sphere.

Problem 5.6 (a) A phonograph record carries a uniform density of "static electricity" o. If it rotates at angular velocity w, what is the surface current density K at a distance r from the center? (b) A uniformly charged solid sphere, of radius R and total charge Q, is centered at the origin and spinning at a constant angular velocity w about the z axis. Find the current density J at any point (r, 0, p) within the sphere.