What prevents a large piece of uranium ore from going naturally into a chain reaction?
a. Because none of its nuclei fission without bombardment from human-controlled sources.
b. Because even a small chunk is too large to sustain a chain reaction.
c. Because the sample is not large enough to capture many neutrons.
d. Because there isn't enough uranium for fissioning neutrons to trigger another reaction.
e. Because so many of its fissioning neutrons are captured by uranium-238 which then decays in other ways.
e
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A Carnot engine runs between a hot reservoir at Th and a cold reservoir at Tc. If one of the temperatures is either increased or decreased by 3.5 K, which of the following changes would increase the efficiency by the greatest amount?
a. increasing Th b. increasing Tc c. decreasing Tc d. cannot be determined from information given
A 2.0-? resistor is in series with a parallel combination of 4.0-?, 6.0-?, and 12-? resistors. What is the equivalent resistance of this system?
A) 24 ? B) 4.0 ? C) 1.8 ? D) 2.7 ?
Which of the beams is due to an energetic light wave?
A) a B) b C) c D) a and c E) all of the above
Infrared waves are often called heat waves because they
40) A) emanate from relatively hot sources. B) consist of frequencies lower than those of visible light. C) induce resonance in molecules and increase internal energy in a substance. D) are the predominant waves emitted by the sun.