Physics · Thermodynamics

One reversible heat engine operates between 1600 K and T2 K, and another reversible heat engine operates between T2 K and 400 K. If both engines have the same heat input and heat output (work outputs are different but efficiency constraints imply a geometric/arithmetic progression based on conditions; here operating as a series combination with equal heat exchange properties or intended ideal relation where work done is equal, T2 = (1600+400)/2 = 1000 K, or if efficiency is equal, T2 = √(1600 × 400) = 800 K. Given the option and core thermodynamic standard problems for same efficiency/heat-ratio), if both engines have the same thermal efficiency, then the temperature T2 must be equal to: