EMF of the cell

The electrochemical cell consists of two half cells. The electrodes in these half cells have different electrode potentials. When the circuit is completed the loss of electrons occurs at the electrode having lower potential whereas the gain of electrons occurs at the electrode having lower reduction potential whereas gain of electrons occurs at the electrode with higher reduction potential. The difference is the electrode potentials of the two electrodes of the cell are termed as electromotive force (abbreviated as EMF) or cell voltage( Ecell). Mathematically, it can be expressed as

EMF = Ered ( Cathode) - Ered ( Anode) or simply as EMF = Ecathode - Eanode 

Since in the representation of a cell, the cathode is written on the right-hand side and the anode on the left-hand side, therefore, EMF of a cell is also sometimes written as EMF = ERight - ELeft = ER- EL


EMF of the cell may be defined as the potential difference between the two terminals of the cell when either no or very little current is drawn from it. It is measured with the help of a potentiometer or vacuum tube voltmeter.

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