emf, pd and voltage confusion

[leeweide]

Hi, everyone. I am very confused over these three terms, electromotive force, potential difference and voltage. Just exactly what is the difference between them? Can anyone explain these in simple terms for me? I need to explain it to a bunch of 14 year old but I can't. Also, if you would not mind, please include a more advanced explanation to me. haha. Thank you.

 

I hope the community can reply as fast as possible. ^^

[thedarkshade]

Electromotive force is the force which appears when converting chemical energy sources into electric energy. It represent the energy converted (W) per amount of electricity (q)

 

Potential difference actually represent tension, voltage, it is exactly the same thing. To have electricity flow you need to have a potential difference, and that represents voltage.

 

[math]\Delta \phi = U[/math]

 

edit: this \phi is not what I really wanted but it works I hope:-)

[swansont]

http://en.wikipedia.org/wiki/Electromotive_force

http://en.wikipedia.org/wiki/Voltage

 

Potential difference and voltage are the same thing; the former is the technical term and the latter is the common use, since potential difference is measured in Volts (it would be the same as if one referred to distance as "meterage" or speed as the "kilometers per hourage"). It's the amount of energy per charge that will be dissipated or gained between two points, e.g. 1 Volt means that 1 Coulomb of charge will lose or gain 1 Joule of energy.

 

EMF is a little different, since it refers to the actual source of potential difference, often in terms of a battery, as thedarkshade had said, but also other sources like a change in magnetic field (giving rise to a "counter EMF" or "back EMF") from Faraday's and Lenz's laws. So the EMF refers to the specific mechanism where that charge gains (or loses) its energy.

 

But the use often gets blurred and EMF is sometimes seen as archaic and identical to the potential difference.