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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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.
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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
Normal matter is baryonic
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