# Magnetic Field in a moving Medium

1. Jan 19, 2010

### Eldgar

I recently learned about the Fizeau experiment,
http://en.wikipedia.org/wiki/Fizeau_experiment[/PLAIN] [Broken]
showing that light moves with a moving medium to an extent.

However i was wondering what would happen with a magnetic field in a moving medium.
would it shift as well.

For example if a magnet was below a moving sheet of steel, would the magnetic field be shifted on the other side of the steel.

Any experiments or explanations on the subject would be appreciated.

Last edited by a moderator: May 4, 2017
2. Jan 19, 2010

### Daveman20

Most high-energy physics experiments use exactly such devices, even though the particle's have so much momentum that they never circle but only curve a few degrees from their straight line trajectories.

Here hope this helps

http://www.pa.msu.edu/courses/1997spring/PHY232/lectures/magforces/circle.html

So maybe if the steel was moving very fast It would have no effect on it. Momentum seems to play a role.

3. Jan 19, 2010

### Daveman20

Anyone else?

4. Jan 21, 2010

### Eldgar

I was hoping there might have been a magnetic field test when the steel is stationary and when it was moving.

The same concept might apply to a material with a high dielectric constant moving at high speeds, and the electric field be effected on the other end of the material.

i will try and show a picture.

this image isn't exactly what i was thinking.

I was picturing the solenoid material moving perpendicular to the flux lines.

But notice how the flux lines are more compressed in the iron core then the air core.
I was wondering if the movement of the iron core would somehow effect the flux lines.
Of course I know if there is movement in the core there will be eddy currents in the material
which will affect the flux lines.
But hypothetically if the magnetic material had an extremely high resistance and moved would there be any effects on the magnetic field.

Last edited: Jan 21, 2010
5. Jan 21, 2010

### Bob S

First, let's consider the following:

1) For example if a magnet was below a moving non-magnetic conducting plate, would the magnetic field be shifted on the other side the non-magnetic conducting plate?.

The magneic field would not be shifted if the magnetic field were uniform everywhere in the conductor. If it were not uniform, eddy currents in the conductor would retard (shift) and attenuate the changes in the magnetic field. The uniform part of the magnetic field will not be affected.

2) For example if a magnet was below a moving steel plate, would the magnetic field be shifted on the other side the steel plate?.

Same as above, if the permeability of the steel were constant (independent of magnetization). There might be a small additional effect (beyond the eddy current effects) due to hysteresis losses in the steel.

It is useful here to consider the effect of a static magnetic field stator (dipole field, quadrupole field) on a rotating (moving) laminated steel armature in a dc generator (with no load). There is no eddy current effect if the laminations are sufficiently thin.

It is also useful to review the properties of homopolar generators (Faraday disks). See the table in

http://en.wikipedia.org/wiki/Homopolar_generator

Bob S