If the external resistance is \(R\) and the internal resistance is \(r\), the total resistance of the circuit is \(R + r\), so that the current that flows is E\(/(R + r)\). If we take the point A as h...If the external resistance is \(R\) and the internal resistance is \(r\), the total resistance of the circuit is \(R + r\), so that the current that flows is E\(/(R + r)\). If we take the point A as having zero potential, we see that the potential of the point B will be E - \(Ir\), and this, then, is the potential difference across the poles of the cell when a current \(I\) is being taken from it.
