Connect Heat-Engine Work and Efficiency - Practice 1

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For a cyclic engine with no net change in stored energy, work output equals heat input minus rejected heat. Thermal efficiency is work output divided by heat input. This ideal bookkeeping does not assert that any proposed temperatures can achieve that efficiency.

Worked example

An engine takes 1000 J and rejects 700 J per cycle. Work is 300 J and thermal efficiency is 30%.

Two bars on the same scale compare input 1000 J with output 300 J. Output is 30% of input. Use the boundaries specified in the worksheet; unused input is not destroyed.

Question 1 Paper cyclic-engine record 1: 1000 J heat enters, 900 J heat is rejected, no stored-energy change. What is thermal efficiency as a percentage? Answer

Question 2 Paper cyclic-engine record 2: 1000 J heat enters, 850 J heat is rejected, no stored-energy change. What is thermal efficiency as a percentage? Answer

Question 3 Paper cyclic-engine record 3: 1000 J heat enters, 800 J heat is rejected, no stored-energy change. What is thermal efficiency as a percentage? Answer

Question 4 Paper cyclic-engine record 4: 1000 J heat enters, 750 J heat is rejected, no stored-energy change. What is thermal efficiency as a percentage? Answer

Question 5 Paper cyclic-engine record 5: 1000 J heat enters, 700 J heat is rejected, no stored-energy change. What is thermal efficiency as a percentage? Answer