Thermodynamic Devices: Suppose that the Department of Energy develops a new reversible engine that has a coefficient of performance (COP) of 4.0 when operated as a refrigerator and a COP of 5.0 when operated as a heat pump. What is its thermal efficiency when operated as a heat engine doing work?
A. 10%
B. 20%
C. 25%
D. 45%
E. 80%
Answer: B
Physics & Space Science
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a. True b. False Indicate whether the statement is true or false
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The places where the Sun crosses the equator are called the
A) annalemmas. B) prime meridians. C) zeniths. D) equinoxes. E) solstices.
Physics & Space Science
Pulsars
A) spin very rapidly when they're young. B) are the cause of gamma-ray bursts. C) spin very slowly when they're young, and gradually spin faster as they age. D) generally form from 25 solar mass stars. E) emit radio in all directions.
Physics & Space Science
If the voltage amplitude across an 8.50-nF capacitor is equal to 12.0 V when the current amplitude through it is 3.33 mA, the frequency is closest to:
A) 32.6 kHz B) 5.20 MHz C) 32.6 Hz D) 5.20 kHz E) 32.6 MHz
Physics & Space Science