# Faraday's law for an infinite magnetic field slab

1. Dec 8, 2009

### ehrenfest

1. The problem statement, all variables and given/known data
The magnitude of an infinite slab of uniform magnetic field is increased. What is the electric field induced by Faraday's Law

2. Relevant equations

$$\nabla \times \mathbf{E} = -\frac{\partial \mathbf{B}}{\partial t}$$

3. The attempt at a solution
Choose any point inside the slab. Because the magnetic field is radially symmetric about that point, the electric field must also be radially symmetric. By radially symmetric, I mean radially symmetric in a plane parallel to the slab planes. But if you choose any other point, the electric field must also be radially symmetric about that point. This can only happen if the electric field points perpendicular to the slab planes. But that violates Faraday's law...I'm confused.

2. Dec 10, 2009

### gabbagabbahey

So am I...what do you mean by "an infinite slab of uniform magnetic field"?...Does the slab extend to infinity in all three dimensions or just 2 or 3? Are you told which direction the uniform field point in?

Please write out the complete original problem statement, word for word.

3. Dec 12, 2009

### ehrenfest

Its a problem I thought up myself. The magnetic field extends out to infinity in two directions (say x and y) and it points in the third direction (z).