What is the emf of a galvanic cell?

I am getting confused between EMF and potential difference of a cell. But i know that when a charge moves against an electric field it's potential energy increases which can be used to do some work. So can i say EMF of the cell is the work done in order to get the required potential difference between the electrodes. And if it is so can you explain the difference between PD and EMF




Potential difference and EMF are equal if the galvanic cell does not produce any currant. When the cell works and produces even a small currant $I$, the potential of the cell decreases a bit, because of the internal resistance $R\_i$ of the cell. If $E\_o$ is the the EMP, the potential $E'$ measured between the plus and the minus poles of the working cell decreases a little bit according to Ohm's law : $E' = E\_o - R\_i I$


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