Thermodynamic Devices: A refrigerator has a coefficient of performance equal to 4.2. How much work must be done on the operating gas in the refrigerator in order to remove 250 J of heat from the interior compartment?
A. 60 J
B. 120 J
C. 250 J
D. 480 J
E. 1050 J
Answer: A
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Force on a Wire: For the horseshoe magnet shown in the figure, the left end is a north magnetic pole and the right end is a south magnetic pole. When the switch is closed in the circuit, which way will the wire between the poles of the horseshoe magnet initially deflect?
A. to the right B. to the left C. upward D. downward
A factory siren indicating the end of a shift has a frequency of 80 Hz. What frequency is perceived by the occupant of a car traveling towards the factory at 30 m/s? The speed of sound in air is 343 m/s
A) 83 Hz B) 85 Hz C) 87 Hz D) 89 Hz E) 91 Hz
The least diffraction occurs for
a. ? < d. b. ? = d. c. ? > d. d. none of these; that is, it makes no difference.
California's Sierra Nevada are examples of ______________ mountains
Fill in the blank(s) with correct word