# Electromotive force

1. Jan 23, 2010

### Basel A

A generator is charcterized by its internal resistance and electromotive force E. What is meant by electromotive force..(plz i need perfect answer)

2. Jan 24, 2010

### Stonebridge

The standard definition (for a generator) would be "The electromotive force of a generator (dynamo) is the amount of mechanical energy converted into electrical energy when unit charge passes through it." (Measured in joule per coulomb or volt)
The generator has to do work to move charge through it; in doing so the charges gain electrical energy. When connected to an external circuit, this energy is converted into other forms, for example heat in resistors, when the charges flow around that circuit.

3. Jan 24, 2010

### Naty1

There is no "perfect" definition.
try wikipedia at http://en.wikipedia.org/wiki/Electromotive_force for a further discussion.
A generator, or alternator, is characterized by a lot more than the two (important) factors you stated.

4. Jan 26, 2010

### Asok

as i have learnt , electromotive force is the the energy requires to drive +1 charge(unit charge) along the path.. say you have a circuit which describes as a closed path with 'no' any resistance... then you dont have any disturbance to drive any charge along that path..that means the required EMF is zero to drive the charges(current).. and this EMF is very much similar as the voltage(well I dont see a much difference)... and for a generator EMF is the same definition and the internal resistance is the resistance inside that generator(independent of the external circuit).. simply EMF is the voltage of the generator... but there is something to consider when you take the open circuit voltage and the effective voltage... open circuit voltage of a gen is higher than the effective one.. (this difference comes bcoz of the internal resis)...sketch a circuit diagram with internal resis... and dont forget EMF is an energy... again take into consideration , if you use EMF to drive charges that energy EMF converts to the energies like heat(in resistors), maybe light(if there are bulbs in the circuit) etc.. because you use EMF against those disturbances(resistors, motor loads etc) and there is something that should be happened to that used EMF energy...(energy conservation).. hope this would be helpful..