Georg Ohm is credited with stating Ohm’s law relating voltage, current, and resistance.
Ohm published his findings in 1827 after investigating how current changed when different voltages were applied to conductors. The law is written V = IR, where V is voltage, I is current, and R is resistance. Rearranging the equation gives the other commonly used forms, I = V/R and R = V/I.
Ohm’s law is especially useful for many metallic conductors over a suitable range of temperatures. Such components are called ohmic when their resistance remains approximately constant under the conditions being tested.
The law is not universal for every electrical device. Diodes, incandescent-filament lamps, and many semiconductor components have resistance that changes with voltage, current, or temperature. Ohm’s research was initially controversial, but his relationship became foundational to circuit analysis.