BitWithBite
Physics Worksheet
⚙️ Heat Engines
SCORE___ / 20
NameClassDate
After this worksheet you can
Understand: How a Heat Engine WorksUnderstand: Efficiency of a Heat EngineUnderstand: The Carnot EngineUnderstand: Why Real Engines Are Less Efficient🧠 Section A · Concept Check ● BEGINNER 4 × 1 = 4
1A heat engine absorbs 2000 J and produces 600 J of work. Find its efficiency.
2Find the Carnot efficiency between Th=800K and Tc=400K.
3Find the Carnot efficiency between Th=1000K and Tc=250K.
4Why does increasing the temperature difference (Th-Tc) generally increase a heat engine's maximum possible efficiency?
🧮 Section B · Problem Solving ● INTERMEDIATE 4 × 3 = 12
5A real engine has efficiency 25%, while its Carnot limit is 40%. What does this gap represent?
6If a heat engine absorbs 1200 J and its efficiency is 35%, find the useful work output.
7Using the previous engine, find how much heat is expelled to the cold reservoir.
8Why must every cyclic heat engine expel some heat to a cold reservoir?
🚀 Section C · Challenge ● CHALLENGE 2 × 2 = 4
9What happens to a heat engine's theoretical maximum efficiency as Tc approaches Th?
10Why are power plants often built near rivers or large bodies of water?
💭 Reflection — the most useful thing I learned:
A ___/4 B ___/12 C ___/4 Total ___/20
Teacher's Signature
Parent's Signature
✂ answer key — fold or cut before handing out
1 = 0.3 or 30% 2 = 1-(400/800)=0.5 or 50% 3 = 1-(250/1000)=0.75 or 75% 4 = The ratio Tc/Th decreases as the temperature difference grows, increasing 1-(Tc/Th) | 5 = Losses due to friction, heat leakage, and other non-ideal (irreversible) effects in the real engine 6 = W=0.35*1200=420 J 7 = Qc=Qh-W=1200-420=780 J 8 = The second law of thermodynamics prevents 100% conversion of heat into work in a repeating cycle | 9 = It approaches 0% efficiency, since the temperature difference driving the engine vanishes 10 = To provide a large, stable cold reservoir for expelling waste heat, improving the practical efficiency of the heat engine cycle