Question

The emf of a cell is always greater than its terminal voltage. Why?

Answer 1

EMF of a cell:

1. The electric potential differences (PDs) caused by charge separation (electrons or ions) at each phase boundary (or interface) in a cell are added together to form the cell's emf.
2. A potentiometer is used to measure emf.

Terminal voltage:

1. When a circuit is turned on, the potential difference across the terminals of a load is referred to as terminal voltage.
2. A voltmeter is used to measure the terminal voltage.

The emf of the cell is always greater than its terminal voltage;

1. Since the potential drop across the cell caused by its low internal resistance, the emf of a cell is higher than its terminal voltage.

Thus, due to low internal resistance, the cell's emf is greater than the terminal voltage.