The source defines a heat pump's coefficient of performance, COPhp, as a ratio of two quantities. Which ratio is it?
AThe work input divided by the heat delivered to the hot reservoir
BThe heat extracted from the cold reservoir divided by the work input
CThe heat delivered to the hot reservoir divided by the work input
DThe hot reservoir temperature divided by the cold reservoir temperature
Answer & Solution
Correct answer: C. The heat delivered to the hot reservoir divided by the work input
1. A heat pump's usefulness is judged by how much heat transfer it delivers compared with how much work must be put in to drive it.
2. The source defines the coefficient of performance as COPhp = Qh / W, the heat delivered to the hot reservoir divided by the work input.
3. Option A inverts this ratio, describing W / Qh instead.
4. Option B describes the different ratio Qc / W, which is instead used later for refrigerators, and option D describes a ratio of temperatures rather than of heat transfer and work.
_Source: OpenStax College Physics (CC BY 4.0), Ch 15 "Thermodynamics", section 15.5 Applications of Thermodynamics: Heat Pumps and Refrigerators_
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