# A large, flat sheet carries a uniformly distributed electric current with current per unit width Js.

A large, flat sheet carries a uniformly distributed electric current with current per unit width Js. This current creates a magnetic field on both sides of the sheet, parallel to the sheet and perpendicular to the current, with magnitude

B = (1/2)μ0Js.

If the current is in the y direction and oscillates in time according to

Jmax (cos ωt) = Jmax[cos (−ωt)]

the sheet radiates an electromagnetic wave. The figure below shows such a wave emitted from one point on the sheet chosen to be the origin. Such electromagnetic waves are emitted from all points on the sheet. The magnetic field of the wave to the right of the sheet is described by the wave function

= − (1/2)μ0Jmax[sin (kx − ωt)].

(a) Find the wave function for the electric field of the wave to the right of the sheet. (Use the following as necessary: μ0c for the speed of light, Jmaxkxω, and t.) =

asked Mar 27, 2012 in Physics
(b) Find the Poynting vector as a function of x and t. (Use the following as necessary: μ0, c for the speed of light, Jmax, k, x, ω, and t.)
=

(c) Find the intensity of the wave. (Use the following as necessary: μ0, c for the speed of light, Jmax, k, x, ω, and t.)
I =

(d) If the sheet is to emit radiation in each direction (normal to the plane of the sheet) with intensity 223 W/m2, what maximum value of sinusoidal current density is required?
A/m

Steps will be updated later...

Part D:

You would solve for Jmax from part C, resulting in:

answered Apr 1, 2012 by ~Expert~ (3,020 points)
selected Apr 1, 2012 by yoshi