# Homework Help: Magnetism in infinite conducting slab

1. Aug 9, 2004

### daveed

"a conducting slab has infinite extent in the x and y directions and thickness L in the z direction. The slab is centered at z=0 and carries a uniform current density J=Ji where i, j, and k are unit vectors in the x, y, and z directiosn."
-Find the magnetic field B at all points.

-A square loop of side a is placed distance b above the slab. The loop has unit normal vector n=sin(q)i+cos(q)j and applied current J. what is the net force and net torque to the loop as a function of q?

-the applied current I is now removed from the loop and the current density in the slab J=Ji is reduced to zero over time T. The wire used to construct the loop has resistance/unit S. How much charge flows through each cross section of the loop wire due to the reduction in current density.

2. Aug 10, 2004

### Locrian

What have you tried so far?

It seems to me ampere's law would work well in determining the magnetic field; use a square loop such that you know exactly how much current passing through it and the only field is at the top and bottom. Integrating a line of wires across the surface and then again through the depth is another option, but sounds horrible to me.

Once you have the magnetic field, the second part should come together easily enough.

3. Dec 9, 2004

### daveed

i really dont know how to go about doing this when its not a single wire... sorry =(

4. Dec 9, 2004

### Tide

Have you considered the integral form of Ampere's Law?

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