College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 68

Two 1.50-V batteries-with their positive terminals in the same direction-are inserted in series into the barrel of a flashlight. One battery has an internal resistance of 0.255 , the other an internal resistance of 0.153 . When the switch is closed, a current of 0.600 A passes through the lamp. (a) What is the lamp's resistance (b) What fraction of the power dissipated is dissipated in the batteries