# Layman explanation of some simple EM equations

## Main Question or Discussion Point

So its been a while since I studied maxwells equations, anyway:

So From my ignorant perspective, trying to derive conceptual meaning from these, I can see that the time dependant study there is some conductivity x the partial differential of the magnetic vector potential plus the cross product of mu*B which is H minus SOMETHING? equals the electron current density.

I don't really remember what the magnetic vector potential is (well, that is to say, I remember not really understanding it when I tried learning about it in the first place), or the last term....or what the cross product of H is.
I'm at a similar loss regarding the Frequeny Domain study.

To be honest all I really remember about the cross product is that it is perpendicular to the two vectors being multiplied.

If any one can offer a more indepth explanation of these formulas in English, I mean some maths is fine, but for a layman, that'd be great.

Cheers!!

## Answers and Replies

Related Other Physics Topics News on Phys.org
These might help

sophiecentaur
These might help
Thanks for the reply, the second vid was a good refresher about curl (and to a lesser extent divergence), The first one didn't tell me anything I didn't already remember, but it made me try and wonder how Faraday's law might fit into those equations? (given that it has a current and cross product of B in it too).
But I'm still none the wiser about what the 'v' is in that equation (velocity?) or what the curl of H, cross product of Bxv and partial derivetive of A have to do with current density??

Cheers!

So am I to assume that these equations aren't a modification/application of one specific Maxwell equation??

jtbell
Mentor
What is the context of those equations? Where did you see them?

They seem to have something to do with electric and magnetic fields and electric currents in conductors. σ is the usual symbol for electrical conductivity, which is the reciprocal of resistivity: σ = 1/ρ.

What is the context of those equations? Where did you see them?

They seem to have something to do with electric and magnetic fields and electric currents in conductors. σ is the usual symbol for electrical conductivity, which is the reciprocal of resistivity: σ = 1/ρ.
Yeah, they're from Comsol Multiphysics, depending on if you're simulating something that varies over time etc.