A solenoid of inductance L = 50 mH has a magnetic energy U = 3 x 10-4 J with a density u = 0.0042 J/ m3. What is the winding density n of the solenoid?
A)
58 turns/m
B)
1584 turns/m
C)
1200 turns/m
D)
234 turns/m
E)
746 turns/m
E
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Which of the following correctly lists two key pieces of evidence that, together, indicate that we should expect human activity to cause global warming?
A) (1) Carbon dioxide tends to make planets warmer than they would be otherwise. (2) Measurements demonstrate that human activity is raising the carbon dioxide concentration in the atmosphere. B) (1) The carbon dioxide cycle regulates Earth's climate. (2) Human activity has disrupted the carbon dioxide cycle. C) (1) The burning of fossil fuels is a form of human activity. (2) Human activity is always bad for the environment. D) (1) We can learn about past climate from ice cores. (2) Ice cores show that Earth naturally has cooler and warmer periods.
How much power does a sphere with a radius of 10 cm radiate if is has an emissivity e = 1.0 and is kept at a temperature of 400 K? The Stefan-Boltzmann constant is 5.67 x 10-8 W/(m2•K4)
A) 60 W B) 70 W C) 180 W D) 210 W E) 360 W
A softball player determines her pitching speed by throwing a ball horizontally from an elevation of 5 m above the ground. The ball lands 20 m downrange. What is her pitching speed?
A) 5 m/s B) 10 m/s C) 20 m/s D) 25 m/s E) none of the above
Two waves approach each other as shown. When they completely overlap, the resulting wave will look like
A. 
B. 
C. 
D. 