Ohm's Law

Georg Ohm published this relation in 1827 after painstaking experiments with wires of different lengths and thicknesses, and was initially ridiculed for reducing electricity to arithmetic. The idea is simple: voltage is the electrical push, resistance is the opposition, and current is what results. Double the push and you double the flow; double the opposition and you halve it. A 12 V car battery connected across a 6 Ω lamp drives 12/6 = 2 A through it; swap in a 3 Ω lamp and the current doubles to 4 A.

The law holds for ohmic conductors at constant temperature: metals, resistors, most wiring. Components like diodes, filament bulbs, and thermistors bend the rule because their resistance shifts as they heat up or as voltage changes. The classic V–I–R triangle mnemonic works because every rearrangement here is a single multiplication or division.