Question

“A low voltage battery from which high current is required must have low internal resistance.” Justify. 

Answer 1

The total voltage provided by a battery is given by:

V = E − Ir

Where all the alphabet are in their usual meanings. From Ohm’s law:

I = `E/((R + r))`

Where R is the external resistance.

For a low-voltage battery, E is small. To achieve a large current, the resistance (r) must be small to ensure that the majority of the voltage is accessible to the external circuit. If r were large, a considerable portion of the battery’s voltage drop would occur within the battery, thereby reducing the current in the external circuit. Thus, low internal resistance ensures that maximum power is sent to the external load rather than being wasted as heat within the battery.