Chapter · Electricity
Volts, amps and ohms
The three numbers everything else is made of, the one equation that ties them together, and the schoolmaster who was called a fraud for finding it.
- 01Where Ohm’s law came from7 minA schoolmaster in Cologne with no laboratory, no assistant and no budget found the rule every circuit obeys, published it in 1827, and was written off as a fraud. It took fourteen years and a foreign medal before anyone agreed, and the unit stamped on your resistors is his name.
- 02Voltage, current, resistance6 minThree words and one equation — voltage pushes, current moves, resistance gets in the way. The part nobody says first is that you only ever get to choose two of them, and the third is decided for you whether you did the sum or not.
- 03Ohm’s law on real problems8 minThe equation takes a minute. Knowing which of the three numbers you are missing takes practice, so here are the three questions it actually gets asked on a bench, with the unknown moved to where it really sits.
Start at 01 and read down — the order is the order things get easier in. Or take the one with your part in it; every article stands on its own, and links back to whatever it needs.