An electronic toy is powered by three 1.58-V alkaline cells, each with an internal resistance of 0.0215 , and a 1.53-V carbonzinc dry cell, whose internal resistance is 0.125 . All four cells are connected in series as part of a single-loop circuit. The resistance of the rest of the circuit is 4.275 .
(a) What current, I, in amperes, flows through the toy's circuit?
(b) How much power, P, in watts, is supplied to the toy?
(c) The dry cell fails in such a way that it maintains its emf while its internal resistance increases greatly. That results in a reduced power of only 0.500 W supplied to the toy. What is the internal resistance, r2,failing, in ohms, of the failed dry cell?