This video starts with an explanation of Ohm's Law. Then, it zeros in on two formulas that are derived from Ohm's Law that are very useful to the homeowner.
I=P/E and P=E X I
Examples are given on how to use these two handy formulas and then they are proven using a simple circuit.
Note: you should always switch the hots (blacks). This kills the power to fixtures when the switch is off making bulb replacements more safe, for example. The board that I used in the show is not wired that way because the plug is not polarized, so either side could be hot - told you it's not up to code!. For clarity though, I probably should have wired it that way. That's what you get when you do wiring while playing with the kids!