The efficiency of Carnot's heat engine is 0.5 when the temperature of the source is T1 and that of sink is T2. The efficiency of another Carnot's heat engine is also 0. 5. The temperature of source and sink of the second engine are respectively :

Efficiency of Carnot's heat engine,η=1−T2T1For first Carnot's heat engine,0.5=1−T2T1For second heat engine, 0.5=1−T2′T1′Efficiency remains the same when both T1 and T2 are increased by same factor Therefore, the temperature of source and sink of second engine are T1′=2T1,T2′=2T2