Engines and Efficiency: Work From Heat

Heat engines turn thermal energy into mechanical work, powering cars, trains, and planes.
They work by letting hot gases expand and push pistons, blades, or turbines.
No engine is 100% efficient—some heat always escapes as waste.
The Second Law of Thermodynamics sets this fundamental efficiency limit.
Steam engines were the first big success, turning boiling water into motion.
Modern jet engines burn fuel to blast hot gases backward, propelling planes forward.
Car engines convert only about a third of fuel’s energy into motion—the rest is heat loss.
Efficiency improves with technology: hybrids, turbines, and electric systems waste less.
Engineers study efficiency to cut fuel use, lower costs, and reduce emissions.
From locomotives to spacecraft, engines prove that heat can do powerful work—though never perfectly.