Recent content by Meir Achuz

What those terms mean physically can only be answered in the context of a physical situation. If you work enough in physics, you will come across physical situations that need those terms. That will answer your question

"I happen to know that information can't travel faster than light" That doesn't apply in nonrelativistic quantum mechanics.

Lenz's law tells you in what direction a loop will rotate when a magnetic field is turned on.

The UC Berkeley yacht club required backward sailing to pass the test to be able to take out boats. This was important, because sometimes you had to back in to the dock because of the funny Berkeley winds. To sail straight back, just keep the tiller pointing toward a fixed point on the shore...

The probability of annihilation is very low until it hits a heavy plate with a large density of electrons.

The equation, $$\nabla\times{\bf H}=4\pi{\bf j}/c$$, contradicts the continuity equation because, $$\nabla\cdot(\nabla\times{\bf H})=(4\pi/c)\nabla\cdot{\bf j}=-4(\pi/c)\partial_t\rho\neq 0$$.

A long magnetized rod looks like two magnetic poles, one at each end. You can find the force law just as you would for two electric point charges. Just calculate how long the length of the rod has to be to have the distant pole contribute only one percent. 1% is fairly stringent, so it is going...

##\nabla_{\vec r}## acts ONLY on ##\vec r##.

Apply the divergence theorem to a surface outside the material where the polarization exists.

If you model the dipole as a plus charge and a minus charge, a distance d apart, you can find the field of each charge by the usual image calculation.

Separation variables works when it works. If it doesn't work, it can often lead to a series solution like the Legendre polynomial expansion.

The McDonald derivation shows that the energy is lost in an RLC circuit. The calculation is much simpler as an RC circuit with L = 0. Since the end result is always the same, the derivation cannot depend on details of the circuit. This is seen in the RLC derivation. This means picking L=0 will...

Lenz's depends on the flux, which changes when a current loop is rotated, so it tells you the direction in which the loop will rotate.

"Deriving twice with respect to time:" I haven't read all the other posts, but there are two different times (t and t') involved.

This sphere will be charged to the extent Q=VR.