The electrical force of a cell or battery called electromotive force (emf). This force, which makes electrons flow around a circuit. Each kind of cell has a particular emf. The size of a cell has no effect on its emf. The chemicals in the cell determines its emf, but large cells last longer than small cells of same basic type. This means that from a large cell, we get a particular em $\mathrm{f}$ for more time as compared to small cell.