Coal fire burning at 1100 k delivers heat energy to a reservoir at 500 k. Find maximum efficiency.

55%

Explanation:

hot reservoir = 1100 K

cold reservoir = 500 K

This is a Carnot system

For a Carnot system, maximum efficicency of the system is given as

Eff = 1 -

where Tc = temperature of cold reservoir = 500K

Th = temperature of hot reservoir = 1100 K

Eff = 1 -

Eff = 1 - 0.45 = 0.55 or 55%