Single-acting vs double-acting steam engine: comparative power output. Context: In a double-acting engine, steam performs work on both sides of the piston each cycle; in a single-acting engine, only one side. Choose the correct comparison of power output for the same size and speed.

ConceptWith identical cylinder size and speed, a single-acting steam engine admits steam to only one side of the piston, producing work on one stroke. A double-acting engine produces work on both strokes. Hence, ideal power of a single-acting unit is about half that of a similar double-acting unit (neglecting small differences in rod area, etc.).