Question

why the efficiency of heat engine cannot be 100%?

Answer 1

The second law of thermodynamics puts a fundamental limit on thethermal efficiency of all heat engines. Even an ideal, frictionless engine can't convert anywhere near 100% of its input heat into work. ... No device converting heat into mechanical energy, regardless of its construction, can exceed this efficiency.

Answer 2

The second law of thermodynamics puts a fundamental limit on thethermal efficiency of all heat engines. Even an ideal, frictionless engine can't convert anywhere near 100% of its input heat into work. ... No device converting heat into mechanical energy, regardless of its construction, can exceed this efficiency.

hope it helps you !#!#!