Question

Problem 3 (25 points): Magnetic Field from Superposition. A circular disk of radius ro is uniformly coated with charge with a surface charge density of ps the disk lies in the x-y plane and the disk axis is the z-axis. This disk is spinning about the z-axis at a rate of one revolution every T seconds. The resulting surface current density on the disk is given by 2Tps a) What is the magnetic field intensity on the z-axis at a point z, above the center of the disk?

Answer 1

"Given that surface change density rho_s disk lines in the x-y plane disk axis is the z-axis revaluation ""7"" seconds the current on the disk can be calculated by the rotating disk to an equivalent to a of concentric current loops. Consider a ring of radius r and width dr as the disk is spinning about z at a rate of revaluation every �t� seconds the surface current density on the disk T_s = 2 pi rho_s/T a^bar phi the field at a distance z due to this ring \r\n db = mu_0/2 (2 pi rho_s a^bar phi rho/T v^2/(r^2 + z_0^2)^3/2 magnetic field at a point along the axis of a current carrying ring] = mu_0/2 I rho^2/(r^2 + z^2)^3/2 where r = radius of the ring z = distance of the pt from the center] if net field is obtained by integrating from v^r = D to r^r - r-a "