Two cells, one of EMF 20 V and internal resistance 1 and another of EMF 5 V and internal resistance 2 , are connected in series such that their positive terminals are joined together. This combination is connected across an external circuit consisting of a 3 resistor in series with a parallel combination of a 12 and a 6 resistor. The terminal voltage across the 5 V cell is ________ V .

Step-by-step solution

The equivalent resistance of the parallel combination of 12 and 6 resistors is: R_p = 12 6 12 + 6 = 72 18 = 4 The total external resistance of the circuit is: R_ ext = 3 + 4 = 7 The total resistance of the entire circuit, including the internal resistances of the cells, is: R_ total = R_ ext + r₁ + r₂ = 7 + 1 + 2 = 10 Since the positive terminals of the cells are joined together, they are connected in opposition. The net EMF of the circuit is: E_ net = 20 V - 5 V = 15 V The total current flowing in the main circuit