Georg Simon Ohm
1789–1854 · 1827
The law that lets you calculate a circuit before you build it
Ohm was a schoolmaster in Cologne, teaching mathematics and physics, working on his own equipment in his own time. He measured how much current a wire carried for a given push, and found the plain relationship every electronics book now opens with: the current is the voltage divided by the resistance.
He published it in 1827 as Die galvanische Kette, mathematisch bearbeitet. It was received badly. The prevailing German philosophy of science distrusted a bare mathematical rule pulled out of experiment, and a critic called it "a web of naked fancies". Ohm resigned his teaching post and spent years in obscurity.
He was vindicated slowly and then completely: the Royal Society gave him the Copley Medal in 1841, and the unit of resistance carries his name.
His law is the arithmetic behind nearly every decision on this board. It is why a resistor sits in front of an LED, and how you know which one to pick.
The thing you can build here
Ohm’s law, by eye →Three resistors across the same battery: watch the current fall as the ohms rise, which is the whole law in one picture.
Sources
- Ohm, Die galvanische Kette, mathematisch bearbeitet, Berlin, 1827.
- Royal Society, Copley Medal, 1841.