College professor just said the following:
"If you are looking at a charge in a magnetic field, and then you make you coordinate system move at the same speed of the charge, then there is no longer a magnetic field. This is needed when studying relativity to eliminate magnetic fields from your calculations. You can also use it in E&M to make your calculations easier."
Is this true? You can't just ignore a significant component of reality can you? She is kinda retarded and like mumbles a lot so maybe she is wrong.
Pic not related, heat treatment.
It's just the principle of relativity.
Look at it this way: a magnetic field is set up between two charged particles if they are moving relative to each other. If you make your coordinate system move with a certain particle, then the magnetic field is zero with respect to any other particle that is also fixed with respect to the coordinate system. In other words, the two particles are not moving relative to each other, so the magnetic field between them should be zero. That makes perfect sense.
It makes calculations easier because now you can eliminate all the terms for particles that are fixed relative to your coordinate system. They're just 0.
Yeah I understand that. But from a practical standpoint I can't design my wire system to run through a magnetic field and say, "oh if I just make my coordinate system move then I don't have to account for the magnetic field in this design."
It is not that the magnetic field disappears, but the effect of the magnetic field on the charged particle will no longer exert a force on it because now the relative velocity between the two is zero, the the magnetic force on the charged particle goes to zero.
There won't be though. Changing coordinate systems takes into account everything. It's literally how you do shit.
You wanna integrate over a surface section of a sphere? You sure as fuck aren't going to use cartesian coordinates for that shit. You convert it. Same principle applies here. You convert your way of looking at something to a way with easier calculations. The conversion takes care of your worries.
> doesn't that just mean you're moving the magnetic field?
Relative to what? That's the question you must always ask yourself.
There is no "stationary" frame of reference that is always correct. Your choice of coordinate system, as long as it is inertial (not accelerating/not experiencing outside forces), is arbitrary. If it's not inertial, then you can measure and correct for that.