resistere

The Latin verb resistere means 'to stand back against' or 'to oppose.' A resistor is any substance that opposes the flow of electric current. Copper conducts electricity easily; it has low resistance. Rubber blocks electricity; it has high resistance. But there was no science of this relationship until Georg Ohm, a German physicist, began experimenting with wires and batteries in Cologne in the 1820s.

In 1827, Ohm published his law: V = I × R. Voltage equals current multiplied by resistance. This was revolutionary. Electrical behavior wasn't mysterious or dependent on vague forces. It followed a simple algebraic rule. Current flows through a conductor in proportion to the voltage applied and inversely to the resistance of the conductor. Measure any two, calculate the third.

Ohm's colleagues ridiculed him. His own employer dismissed his work as meaningless. Ohm was so discouraged by the rejection that he left teaching for five years, convinced his career was finished. He published his findings in German, which limited their reach. But by the 1840s, other physicists—particularly in Britain and France—began replicating his experiments and confirming his law. The scientific community had been wrong.

In 1851, near the end of his life, Ohm was offered a professorship in Munich. He had been vindicated. After his death, his name became immortal: the unit of electrical resistance is the ohm (Ω). Every component that resists electrical flow—every resistor in every circuit—is named in honor of a man whose community once thought him worthless.