Elektromotorische kracht

Alessandro Volta, inventor of the battery, coined the term electromotive force or emf.

Emf is not a force, but rather a potential difference between the two terminals of a battery.

Emf represented by the symbol epsilon, is the maximum voltage a battery can deliver in an open circuit. It is expressed in units of volt.

When a wire is connected between the two terminals, the emf pushes the electrons from the negative terminal to the positive terminal.

Emf is defined as the amount of work done to move a unit charge across the terminals.

In a closed circuit, the voltage measured across the battery's terminals is defined as its terminal voltage, which is always less than the emf value. This is because the battery has an internal resistance r.

The terminal voltage is thus, the difference between its emf and the voltage drop across the internal resistance.