Check Test - Thermodynamics
1 The first law of thermodynamics is a particular expression of the law of ...
a ... mass cation.
... conservation of energy.
2 The internal energy of a mass of gas enclosed in a cylinder depends on ...
... the temperature only.
3 When a gas is heated in a cylinder and does external work, the first law of thermodynamics is written as ...
... DQ = DU +DW
4 When an iceberg melts the change in entropy is ...
... positive
5 The latent heat of fusion when ice melts is 334 000 Joules per kilogram.
The entropy change when one kilogram of ice melts is ....
... 1200 Joules.
6 Which of the following processes is described as reversible?
... a tire is slowly inflated.
7 Which of the following processes can be described as adiabatic?
... a decompression cloud suddenly forms as a plane breaks the sound barrier.
8 A warming pad is activated by exposing a gel, that exists in a metastable state, to a tiny piece of gold foil that acts as a catalyst and initiates a slow exothermic crystallization process. After the pad has been used it is placed in boiling water, the crystals melt once again, and the pad is "recharged".
The exothermic process is ...
... neither isothermal not adiabatic.
9 A mass of polyatomic gas is contained in a cylinder fitted with a piston.
Which of the following processes leaves the internal energy of the gas unchanged (DU = 0)?
The gas is compressed isothermally.
10 The units of area on a PV diagram are ...
... N m.
11 The reversible changes as an ideal gas is taken slowly around the Carnot cycle are in order.
... isothermal compression, adiabatic compression, isothermal expansion , adiabatic expansion.
12 A Carnot engine is ...
... more efficient than any other type of engine.
13 A Carnot engine is 100% efficient ...
... only if the lower temperature is -273°C.
For Questions 14-20 refer to the PV diagram below.
14 A cycle is shown on a PV diagram.
The isobaric process is ....
... c only
15 Which process cannot be adiabatic?
The change that leaves the internal energy of the gas unchanged is ...
... a only
16 If the three processes are all isothermal, for which ones is the heat flow in to the system?
... a and b only.
17 The work done by the gas during the cycle is zero during which process?
... a only
18 The cycle shown is the working cycle of Jacobs reciprocating engine.
The engine is ....
... less efficient than a Carnot engine at all temperatures.
19 The power stroke(s) of the engine is/are ...
... b only.
20 The work done by the engine during the cycle is ....
... the area under process b minus the area under process c.
21 An air conditioner and a refrigerator are ....
... the same machines.
22 A refrigerator has a power input of 2000 Joules per second and transfers 500 Joules per second from a cold box at 10°C to a room at 30°C.
The coefficient of performance for the refrigerator is ...
... 0.25
23 A heat pump is a desirable option for heating a house in winter because ...
... heat pumps transfer heat to the house from two sources and thus avoid the waste of energy.
24 The second law of thermodynamics does not apply ....
... none of the above.
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