# Magnetic Field due to rotating disks

1. Jan 3, 2009

### E&M

1. The problem statement, all variables and given/known data
There are two rotating disks which rotate with angular velocity omega in the same direction about a z axis. Will the magnetic field at the center of those two disks cancel out or will it be twice the field due to one of the disks? This is a part of a bigger problem. So, I haven't posted the relevant equations and attempt as I have already figured out other things. Thanks in advance.

2. Relevant equations

3. The attempt at a solution

2. Jan 4, 2009

### gabbagabbahey

What field point(s) is this question in regard to? Unless the two disks are superposed, the fields will neither completely cancel or double at all field points. However, there are some points at which one of those will happen.

Are the disks identical (do they carry the same charge density?)? Assuming the question is about a point on the z-axis, you can use the right hand rule to determine the direction of each constituent field and then use the superposition principle to determine whether they cancel or double.