What is electromotive force?

EMF (ε) is the total energy supplied by a source per unit charge as it drives charge around a complete circuit.

• Unit: Volt (V) not a force, it is energy per charge.
• EMF = maximum terminal voltage when no current flows (open circuit).

EMF vs. Terminal Voltage: Terminal Voltage = EMF − I × r (internal resistance)

Sources of EMF: Batteries, generators, solar cells, thermocouples.

EMF is the total energy provided per coulomb of charge by an electrical source, representing its maximum ability to drive current.