A cell of emf 1.5 V is connected across an external resistor of 4 . If the terminal potential difference measured across the cell is 1.2 V , the internal resistance of the cell is:

Step-by-step solution

The current i flowing through the external resistor is given by Ohm's law: i = V R i = 1.2 4 = 0.3 A The terminal potential difference of a discharging cell is related to its emf and internal resistance by: V = E - ir Rearranging for the internal resistance r : ir = E - V r = E - V i r = 1.5 - 1.2 0.3 = 0.3 0.3 = 1.0 Answer: 1.0