How does the internal resistance of a cell affect its performance?

The internal resistance of a cell reduces its efficiency by causing a voltage drop when current flows.

The internal resistance of a cell is a crucial factor that affects its performance. It is an inherent property of the cell, which is due to the materials and construction of the cell. When current flows through the cell, the internal resistance causes a voltage drop, which reduces the cell's efficiency. This is because the cell has to work harder to maintain the same output voltage, leading to faster depletion of its chemical energy.

The internal resistance of a cell is typically very small, but it can become significant when the cell is supplying a large current. This is because the voltage drop across the internal resistance is given by Ohm's law, V=IR, where V is the voltage drop, I is the current, and R is the internal resistance. Therefore, the voltage drop (and hence the loss of efficiency) increases with the current.

Furthermore, the internal resistance of a cell can increase over time due to chemical changes within the cell. This can lead to a decrease in the cell's performance, even if the cell is not being used. For example, if a cell is left in a device for a long time without being used, its internal resistance can increase, leading to a decrease in its voltage and hence its ability to power the device.

In practical applications, the effect of the internal resistance of a cell can be minimised by using cells with a low internal resistance, or by using cells in parallel. When cells are connected in parallel, the total internal resistance is reduced, which reduces the voltage drop and increases the efficiency of the cell.

In conclusion, the internal resistance of a cell is a key factor that affects its performance. It causes a voltage drop when current flows, which reduces the cell's efficiency and can lead to faster depletion of its chemical energy. Therefore, understanding the internal resistance of a cell is crucial for optimising its performance.