The law stating that current through a conductor is directly proportional to the voltage across it is Ohm’s law.
For an ohmic component held under suitable conditions, Ohm’s law is written V = IR, where V is voltage, I is current, and R is resistance. If resistance remains constant, doubling the voltage doubles the current. The law is therefore a relationship among three circuit quantities, not a claim that every component behaves linearly in every situation.
German physicist Georg Ohm published the experimental work behind the law in 1827. His measurements examined how voltage, current, and the properties of wires were related. The modern equation is now fundamental to circuit analysis and can also be expressed as I = V/R or R = V/I.
A common mix-up is assuming that all conductors are perfectly ohmic. Diodes, filament lamps, and many semiconductor devices have nonlinear current–voltage behavior. Their resistance can change with voltage, current, or temperature, so Ohm’s law may only provide a local approximation or may not apply in its simple form.