# Magnetic Field

1. Aug 20, 2014

### D.R.U

How magnetic field associate with mass........
from the experiment we know that this is due to electric charge.....
So is this another property of charge which come in front when charged particle goes in motion?....

Is this associate with mass or electric charge or with both?

2. Aug 21, 2014

### ChrisVer

I don't really understand your first question... there is no connection between the mass and the magnetic field... the one is a property of particles the other is a part of the electromagnetic field.
Some magnetic field is equivalent to an some electric field in another reference frame (or in Special Relativity, the electric and magnetic field are just the two sides of the same coin -electromagnetism)

3. Aug 24, 2014

### Maharshi Roy

In field theory, it has been described that the particle of electromagnetic field is a photon. Although photons are massless particles, but they can have relativistic mass when they approach the speed of light. So, in this sense there might be some relationship between magnetism and mass.

4. Aug 24, 2014

### ChrisVer

That is wrong in every phrase... The mistakes:
1."they approach the speed of light." That is actually wrong. Photons don't approach the speed of light, they run with the speed of light, because they are massless.
2."they can have relativistic mass." The relativistic mass is not a nice quantity to talk about, because it is frame-dependent and so physicists hardly ever use it. The rest/invariant mass is the way to walk. The rest mass of the photon is 0 and in fact you can't find any reference frame in which the photon would have some mass.
Even if you wanted to find the relativistic mass (although that's wrong to try for particles travelling at null-wordlines), you wouldn't be able to, because it's $m_{rel}= \gamma m_{inv}$... if $m_{inv}=0$ then you are getting infinity times zero.

Last edited: Aug 24, 2014