What is e.m.f. of a cell ? On what factors does its value depend ?

Explanation

Electromotive force (em): It is the difference of potential between the two terminals of a cell when no current is withdrawn from it.
Factors on which value of emy depends :
1. Nature of electrodes:
2. Nature of electrolyte
It does not depend upon the shape or size of the cell.
Relation between emf (E), contact potential (V), internal resistance (r) and external resistance (R)