Question

The potential difference between the terminals of a 6.0 V battery is 7.2 V when it is being charged by a current of 2.0 A. What is the internal resistance of the battery?

Answer 1

Given:
Potential difference across the terminals of the battery, V = 7.2 V
Emf of the battery, E = 6 V
Current flowing through the circuit, i = 2 A
As the battery is getting charged, the voltage drop across the terminals of the battery will be equal to the emf of the battery plus the voltage drop across the internal resistance of the battery.
So, V = E + ir
⇒ 7.2 = 6 + 2 × r
⇒ 1.2 = 2r
⇒ r = 0.6 Ω