A piston compresses a gas, while at the same time heat is lost to the surroundings. The temperature of the gas rises. The amount of temperature rise is governed by
a. the first law of thermodynamics.
b. the second law of thermodynamics.
c. specific heat capacity.
d. a heat pump.
e. none of the above.
[Ques. 2] The efficiency of a heat engine
a. can never exceed the Carnot efficiency.
b. can be improved by lowering the temperature of the cool reservoir.
c. can be improved by raising the temperature of the hot reservoir.
d. all of the above
[Ques. 3] In a steam engine, steam at 140C in a turbine does work on an external system, and the steam leaves the turbine at 100C. The efficiency of the steam engine is 5. The relevant physical principle is
a. the first law of thermodynamics.
b. the second law of thermodynamics.
c. specific heat capacity.
d. operation of a heat pump.
e. none of the above.
[Ques. 4] Even when the temperature of a pan of water is below the boiling point, some water still evaporates. This is because
a. of convection.
b. the kinetic energies of individual water molecules vary above and below the average value.
c. the humidity always increases.
d. none of the above
[Ques. 5] Air at a temperature of 32 F has a relative humidity of 60. If the temperature of the same air rises to 40 F, the relative humidity
a. stays the same.
b. increases.
c. decreases.
d. cannot be determined.
[Ques. 6] At 96 F the saturation density of air is 0.04 kg/m3 . If the weather report says the relative humidity is 90 when the temperature is 96F, the humidity is
a. 10 .
b. 0.9.
c. 0.004 kg/m3.
d. 0.036 kg/m3.
e. 0.04 kg/m3.
[Ques. 7] Why do bridges have expansion joints?
a. They would buckle and crack otherwise.
b. to let water run off
c. to absorb vibrations due to traffic
d. for ease in construction
[Ques. 8] The Eiffel tower in Paris is made primarily of iron, whose coefficient of linear expansion is about 10 106/C. On a cold day when the temperature is 10C the Eiffel tower is 300 meters tall. Its height on a hot day when the temperature is 40C is
a. 300.0015 m.
b. 300.015 m.
c. 300.15 m.
d. 301.5 m.
e. 315 m.
[Ques. 9] specific heat capacity of ice = 2,000 J/kg-C latent heat of fusion of water = 334,000 J/kg specific heat capacity of water = 4,000 J/kg-C After the 1 kg block of ice melts, the amount of heat required to raise its temperature to 10 C is
a. 2,000 J.
b. 4,000 J.
c. 20,000 J.
d. 40,000 J.
e. 334,000 J.
[Ques. 10] specific heat capacity of ice = 2,000 J/kg-C latent heat of fusion of water = 334,000 J/kg specific heat capacity of water = 4,000 J/kg-C As the ice is melting, the temperature of the ice-water mixture rises by
a. 0C.
b. +5C.
c. 5C.
d. +10C.
e. 10C.
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