3. There are five cells combined in series to form a battery. A light bulb with a resistance of 4 ohms is attached to it and the power is 1.5 A when the light bulb is replaced by an electric fan with...

3. There are five cells combined in series to form a battery. A light bulb with a resistance of 4 ohms is attached to it and the power is 1.5 A when the light bulb is replaced by an electric fan with 9 ohms resistance the power is 0.75 A. Find the internal resistance of each cell.