A certain thermodynamic engine extracts 1.30 kJ of thermal energy from a hot temperature reservoir and discharges 0.70 kJ of energy to a cold temperature reservoir. What is the efficiency of this engine?
A) 46%
B) 54%
C) 86%
D) 27%
E) 13%
A
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When you compress air with a tire pump, the air temperature in the tire
A) increases. B) decreases. C) remains unaffected. D) none of the above
By convention, the direction of current in a circuit is
A) from the positive terminal of a source to the negative terminal. B) the direction in which positive charge flows. C) both of these D) neither of these
In the context of Earth's climate history, what do we mean by snowball Earth?
A) This term is used to describe all the ice ages that have occurred in the past few million years. B) It refers to a time when polar regions had much more snowfall than normal. C) It is what we expect to see happen on Earth in about a billion years. D) It refers to a very deep ice age that occurred hundreds of millions of years ago.
Magnetic reversals of the Earth's field have occurred on the average every 200,000 years over the past 5 million years. When was the last magnetic reversal?
a. about 200,000 years ago c. about 990,000 years ago b. 1792 d. about 780,000 years ago