No internal resistance : terminal pd = emf
With internal resistance :terminal pd not equal to emf if current flow through
With internal resistance : terminal pd equal to emf if no current flow through
Case 1: terminal pd less than emf , battery is discharging ie. Current flowing leftwards ie. out from + terminal
Case 2:terminal pd greater than emf , battery is charging ie. Current flowing rightward ie. into the + terminal.
Between the terminals of the battery contains chemical energy that increases the potential of the charges but at the same time loses some potential due to resistance (internal) in the direction of current flow.
Eg. emf = 1.5 V, r=1ohm , current = 0.5 A
Current flow to the left (discharging) : 1.5 - 0.5 = 1.0V
Current flow to the right (charging) : 1.5 +0.5 = 2.0 V
