Heat added is not all converted to work
- 01
The tempting model
Assuming an engine turns all input heat into useful work.
- 02
Why it feels right
Energy is conserved, so it seems it should all be usable.
- 03
Where it breaks · how to catch it
Your efficiency came out at or above 100%.
- 04
The correct model
First law: ΔU = Q − W. The second law caps efficiency below 1 — some heat must be rejected to a cold reservoir.
- 05
Repair · see it, then test it
worked example An engine absorbs 100 J. Can it do 100 J of work per cycle?
Tempting move
Yes — energy is conserved.
Correct move
No — it must exhaust some heat; efficiency < 100%.
Test the repair TH-02 · transferinclude JMake a fresh prediction before referring to the worked example.