What is Ohm's law?

Ohm's law: V = I × R (voltage = current × resistance, so current = voltage ÷ resistance). Push harder and more current flows; make the path narrower and less flows. For a wire or resistor at a steady temperature, the current is exactly proportional to the voltage, and the number that links them is the resistance.

Read how it works: What is Ohm's law? · The history of Ohm's law · More boxes on Glassbox

Chapters in this interactive model

1. Push, flow and squeeze: Current = voltage ÷ resistance. Turn the dials and watch it hold.
2. Resistance makes heat: Heaters are resistors on purpose. Old fan regulators were resistors by accident.
3. Big currents need fat cables: Every wire has a little resistance. At 60 or 150 amps, a little is a lot.
4. When current turns dangerous: An MCB protects the wires. An RCCB protects you. Both are counting amps.
5. When the line bends: Hot filaments, LEDs and superconductors: where Ohm’s law stops being simple.