Georg Ohm

1789-1854

The German schoolteacher who measured his way to the single most useful equation in electronics: voltage equals current times resistance, the rule every multimeter reading and resistor calculation still rests on.

Georg Simon Ohm was born in 1789 in Erlangen, in what is now Germany, the son of a self-taught locksmith. His father had no formal education but had taught himself enough mathematics, physics, and philosophy to bring Georg and his younger brother Martin to a high standard at home. That homegrown rigor mattered more than the schooling: a professor at Erlangen later compared the two Ohm boys to the famous Bernoulli family of mathematicians. Georg drifted through years as a schoolteacher, often poor and frustrated, while teaching himself from the works of Euler and Laplace.

His breakthrough came at a Jesuit school in Cologne that happened to have a well-equipped physics lab. Working with the brand-new electrochemical cell that Alessandro Volta had invented, and building much of his own apparatus by hand (his locksmith father's influence showing), Ohm started measuring how current flowed through wires. He found that the current through a conductor is directly proportional to the voltage across it, and inversely proportional to its resistance. That clean relationship, voltage equals current times resistance, is now simply called Ohm's law.

He laid out the full theory in his 1827 book The Galvanic Circuit Investigated Mathematically. It was received coldly at the time. His own college did not appreciate the work, and Ohm resigned in disappointment. Recognition came slowly: the Royal Society awarded him the Copley Medal in 1841, he became a foreign member in 1842, and only near the end of his life did he reach the professorship at Munich he had long wanted. He died in 1854.

For anyone building circuits, Ohm's law is the first tool you reach for and the last one you put down. Sizing a current-limiting resistor for an LED, working out how much voltage a sensor drops, checking whether a trace can carry the current you are pushing through it, reading a resistance off a multimeter: all of it is V = I times R rearranged. His name became the SI unit of resistance, the ohm, with the symbol omega. Every resistor you place and every measurement you take is a small act of paying him back.

Fun facts

Ohm built most of his own measuring equipment by hand, drawing on the practical mechanical skills he picked up as the son of a locksmith. He had no fancy lab to start with, just wire, a Volta cell, and a knack for making instruments precise enough to reveal a clean proportional law.
His great work was met with such indifference that he quit his teaching post in disgust. The Copley Medal and real fame only arrived more than a decade after publication, a reminder that being right is not the same as being believed on time.
Henry Cavendish had actually discovered the same current-voltage relationship years earlier, but he never published his electrical work, so it stayed unknown until 1879. By then Ohm had independently found and published it, which is why the law and the unit carry his name and not Cavendish's.