Electromotive Force
- The electromotive Force (e.m.f.) is the name given to the potential difference of the power source in a circuit
- It is defined as
The electrical work done by a source in moving a unit charge around a complete circuit
- Electromotive force (e.m.f.) is measured in volts (V)
Electromotive Force in a Circuit
The EMF is the voltage supplied by a power supply: 12 V in the above case
- The definition of e.m.f. can also be expressed using an equation
- Where
- E = electromotive force (e.m.f.) (V)
- W = energy supplied to the charges from the power source (J)
- Q = charge on each charge carrier (C)
Note: in circuits the charge carriers are electrons
- This equation should be compared to the definition of potential difference (below) as the two are closely related