Voltage or
the terminal potential difference of a
battery or a
generator when it delivers a
current I is related to its
electromotive force ε and its
internal resistance r as follows:
1. When delievering currrent (on discharge)
Terminal voltage = emf - voltage drop in internal resistance or V = ε - Ir
2. When receiving current (on charge)
Terminal voltage = emf + voltage drop in internal resistance or V = ε + Ir
3. When no current exists:
Terminal voltage = emf of battery or generator