Voltage (potential difference) is the energy given to each coulomb of charge as it moves between two points.
- Symbol: V
- Unit: volt (V)
- Formula: V = W / Q (W in joules). 1 volt = 1 joule per coulomb.
A battery or power supply provides the voltage that pushes current around a circuit. Typical values: AA cell 1.5 V, USB 5 V, Arduino UNO logic 5 V, car battery 12 V.
Voltage is always measured between two points. When we say "5 V at a pin", we mean 5 V relative to ground (GND, 0 V).