# Particle in motion

1. Jan 14, 2008

### String_man

As we already know, a moving charge particle develops magnetic field arround itself. That mean to say, inorder to develop magnetic field arround itself a charge particle have to move. Now, lets keep the particle(charge) at rest w.r.t laboratory frame and then we starts to move; as we does so the particle will set into motion from our frame of reference, will it then develops magnetic field arround it then also?

2. Jan 14, 2008

### HallsofIvy

Yes, that is the observation, together with Maxwells equations that came from it that lead to the Michaelson-Morley experiment and to relativity.

"Gallilean Relativity" was based on the idea that "F= ma": if you are inside a closed carriage moving with no acceleration then you cannot do any experiment inside the carriage that will tell you how fast you are moving or even if you are moving. All motion must be relative to something else.

The fact that the magnetic field of a charged particle depends on its speed rather than acceleration implied that you could determine an absolute speed, not relative to any other frame from an experiment involving electro-magnetic fields. That was what the Michaelson-Morley experiment was intended to do.

3. Jan 14, 2008

### dst

These are just the weirdest things, I guess it's analogous to centrifugal force popping up out of nowhere. Hard to get my head round it.

So that of course means no magnetic repulsion between two particles of the same charge moving at the same speed in the same direction?

Last edited: Jan 14, 2008