Consider the loop of flexible wire shown below. If we pass a current through the loop, will it tend to expand (becoming more circular), scrunch up even more tightly, or do nothing?
A. Expand
B. Scrunch up
C. Do nothing
D. The answer depends on the current’s direction.
A. Expand
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Angular momentum plays an important role in star formation. Which of the following characteristics of a protostellar system is probably not strongly affected by the star's angular momentum?
A) the onset of core hydrogen fusion B) the existence of protostellar jets C) the strength of protostellar winds D) the formation of a protostellar disk
A heat pump absorbs heat from the atmosphere at a rate of 30 kW. If work is being done to run this heat pump at a rate of 7.7 kW, what is the coefficient of performance (COP) of the heat pump?
A) 22 B) 0.26 C) 2.9 D) 4.9 E) 3.9
Olbers' paradox asks
A. Why isn't the night sky bright as day? B. How can the Universe be younger than some of the stars in it? C. If dark matter is dark, how can we ever see it? D. Which is the simplest cosmological model?
In very general terms, how do the temperature structures of the atmospheres of Venus and Mars differ from that of Earth?
A) They lack X-ray absorbing thermospheres. B) They lack ultraviolet-absorbing stratospheres. C) Their atmospheres are similar in structure to Earth's, but with much higher temperatures. D) Temperatures in their tropospheres increase with altitude, rather than decreasing with altitude.