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Why the First Law is not enough

Why the First Law is not enough

Schematic of a heat engine with hot source TH supplying QH to an engine, useful work W leaving, and waste heat QC flowing to cold sink TC

The First Law says energy is conserved, so by itself it does not forbid an engine from turning all of its input heat into work. Real engines never do this, so another rule is needed.

Second Law and engines (A-level only) Lesson

  1. A Level
  2. /Physics
  3. /Second Law and engines (A-level only)

Step-by-step lessons on AQA A Level Physics Second Law and engines (A-level only). Each one builds up to exam-style questions. Physics is one of the most mathematically demanding A Levels -- at least 40% of the marks require maths skills at Level 2 (GCSE) standard or above, so build calculation and graph-handling fluency alongside the conceptual content from the start.

Lessons