Understanding Electromotive Force (emf)

[Peter G.]

Hi,

I am learning about emf. I understand that it is the Work done per unit charge to move it around a circuit.

However, reading my book, I got a bit confused. It started to explain a bit about how a battery functions. From what I understand, chemical reactions do work in order to force electrons to concentrate on the negative side of the battery. This, thereby, establishes an electric field.

So, the work in the definition of an emf is the work described above? Electrons from the negative terminal of the battery then flow through the wires, repelling the delocalized electrons?

I am confused!

Thanks in advance.

 

[Simon Bridge]

The battery does physical work to get an electron from the positive terminal to the negative one ... though, in electric circuits, you'd normally think in terms of positive charges. The electron happily falls towards the positive side even in a vacuum. You can think of the batter as like a pump, sucking a charge from the wire at one end and pushing another one out into the the wire at the other end.

That provides the EMF - which, you'll see, is the same as the potential difference between the terminals. The EMF is thought of as driving the charges around the circuit. It's a bit of a misnomer since it does not have the dimensions of Force.