Question

Distinguish between emf and terminal voltage of cell.

Answer 1

Hint:Electro Motive Force or EMF, is not a force as the name suggests, but it is the potential difference that acts between two electrodes. It is widely referred to as a force because it acts as the initial force to begin the flow of charge. Terminal voltage is also a potential difference, but it is enabled between terminals only when the circuit is switched on.

Complete step by step answer:
Terminal voltage is the potential difference across the terminals when the circuit is switched on.Whereas EMF is the maximum potential difference that a cell or a generator is able to produce when there is no current flow across it.When the terminal voltage is measured using a voltmeter, the electro motive force is measured using a potentiometer.The value of the terminal voltage is always lower than that of EMF due to the potential drop that occurs due to the current that passes through the internal resistance of the cell. EMF is the characteristic constant of a cell whereas terminal voltage doesn’t maintain consistency.
We can relate emf (E) and terminal voltage (V) as
E = V + Ir
Where I = current and r = internal resistance of the cell

Note:EMF of the cell can also be referred to as the total work done per coulomb of electricity in a circuit in which the cell is connected, as the work done per unit charge or coulomb is nothing but the potential of the region, irrespective of resistance.