College Physics III – Thermodynamics, Electricity, and Magnetism
Definition
A perfect engine is a hypothetical thermodynamic engine that operates with 100% efficiency, converting all absorbed heat into work without any waste energy or entropy increase. Such an engine violates the Second Law of Thermodynamics and cannot exist in reality.
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A perfect engine would defy the Kelvin-Planck statement of the Second Law of Thermodynamics.
It implies zero entropy change during its cycle, which is impossible for real processes.
No real engine can achieve 100% efficiency due to inevitable losses like friction and heat dissipation.
The concept of a perfect engine helps illustrate why perpetual motion machines are unfeasible.
Understanding the limitations imposed by real engines allows better design and optimization within those constraints.
Review Questions
Why can't a perfect engine exist according to the Second Law of Thermodynamics?
What is the significance of entropy in ruling out the possibility of a perfect engine?
How does the concept of a perfect engine help in understanding real-world thermodynamic systems?
Related terms
Second Law of Thermodynamics: States that total entropy always increases over time for an isolated system, and it is impossible to convert all heat into work without some energy loss.
Carnot Engine: A theoretical model that defines the maximum possible efficiency any heat engine can achieve, operating between two temperatures.
Entropy: A measure of disorder or randomness in a system; it quantifies irreversible energy dispersal at a given temperature.