Heat engines and their efficiency
Answers are for parents and teachers.
1
An engine takes 1200 J from the heater and gives 900 J to the cooler. Find A (J) and η (%).
A = 300 J, η = 25 %
2
An engine of efficiency 35 % takes 2000 J from the heater. Useful work (J)?
700
3
η_max (%) of an ideal engine with T₁ = 800 K and T₂ = 400 K?
50
4
In which stroke of an internal combustion engine is work delivered, and why?
In the power stroke: the mixture burns and the hot gas expands and pushes the piston.
5
Why is a cooler necessary for an engine to work?
To repeat the cycle the gas must return to its initial state, which requires giving part of the heat to the cooler.