[AnimalMuppet]

Maxwell had 20 equations for electromagnetism, because he didn't use vector notation, so he had to do the equations component by component. But that had nothing to do with having multiple theories. The current "Maxwell's equations" are exactly the same as Maxwell's 20 equations, merely expressed in a more convenient form.

[cma]

Wikipedia claims: "Less well known is that Heaviside's equations and Maxwell's are not exactly the same, and in fact it is easier to modify the latter to make them compatible with quantum physics.[25]"

[zardo]

In geometric algebra it's a single equation. ∇E=∂B/∂t

[orbifold]

Actually you can unify E and B into a closed two-form F and get in vacuum

dF = 0

d★F = ★j

Where j = rho dt + jx dx + jy dy + jz dz is the charge and current density, ★ is the Hodgestar operator and d is the exterior derivative. The equations in a medium are slighly less elegant.

[ngoldbaum]

And if you write the electromagnetic field in terms of the 4-vector potential, it's just \Box{A_μ} = 0 (where Box is the D'Alembertian operator). Then again, this doesn't really mean anything without the context of what the notation means...

Feynman has a discussion about this in Volume 2 of the Feynman Lectures: http://www.feynmanlectures.caltech.edu/II_25.html

(I still can't get over how awesome it is that I can deep-link into the Feynman Lectures!!)

[viola11]

That's a charge that applies equally well to the standard formulation and I made this comment just to say that it IS cool you can deeplink the Feynman lectures!

[Tycho]

what is B?

[swombat]

http://www.maxwells-equations.com/ will answer all your questions... :-)

[carbocation]

Amplitude of the magnetic field.