[Coda]

Originally Posted by Potironette

Ohh, so that's what the distance means!

I see! I'd been confusing "charging by induction" with "induction."

There's a formula for that :o. energy lost = current * something?

Actually, it's P=IV again! A current of I amperes passing through a resistor with a voltage drop of V volts generates P watts of heat -- that is, P joules of heat per second. When you talk about a 1000 watt heater or a 100 watt incandescent light bulb, this is exactly what it's talking about.

There's another way to express it: P = I²R, where R is the resistance in ohms. These are related by Ohm's Law, I = V/R, which means that resistance reduces the current produced by a given voltage.