Internal resistance is the electrical resistance inside primary cell and batteries that can limit the potential difference that can be supplied to an external load. [OR]

It is the resistance offered by the electrolyte of a cell to the flow of current between its electrodes.

Explanation:

Internal resistance of a cell is offered by the electrode and electrolyte which oppose the current flow inside the cell. The higher the internal resistance, the less current the battery is capable to provide. A freshly prepared cell has low internal resistance and this increases with ageing. Batteries that have high internal resistance will take more time to fully charge.

The concept of internal resistance is useful for analysing many types of electrical circuits. The strength of the current obtained from a cell depends not only on the emf but also on the internal resistance. Elevated internal resistance measurements can be a sign that a cell is nearing failure.

The internal resistance of a Lechlanche cell is about 5 to 10 ohms.

The internal resistance of a dry cell varies from about 0.5 to 1.0 ohms.