Potential Energy

Here total electrostatic potential energy is zero ie, On solving,

Step 1: Use the formula for current.
The total resistance in the circuit is the sum of the internal resistance and the external resistance . Using Ohm's law: where is the current, is the emf of the cell, is the internal resistance, and is the external resistance.
Step 2: Set up equations for both conditions.
For the first condition, when and : For the second condition, when and :
Step 3: Solve the system of equations.
From the first equation: From the second equation: Equating the two expressions for : Solving for : Thus, the internal resistance of the cell is: