1. An adiabatic free expansion is a process in which a) the pressure remains con
ID: 2035836 • Letter: 1
Question
1. An adiabatic free expansion is a process in which a) the pressure remains constant. b) internal energy decreases. c) the volume remains constant, d) entropy remains constant. e) no heat is transferred between the system and its surroundings. 12. A refrigerator is set in the middle of an insulated room, is plugged in, and is running with its door open. The high temperature reservoir for the refrigerator is the air in the room. What happens to the temperature of the room? a) It goes up. b) It goes down. c) It remains the same. d) It depends on the refrigerator thermostat setting.Explanation / Answer
11) Answer : (e) = no heat is transferred between system and surrounding.
explainantion : since the process is adiabatic free "expansion", there has to be change in volume and pressure. Word "adiabatic" reveals that there is no heat transfer (from or to) involved. Since this process does not involve any heat transfer or work, the first law of thermodynamics then implies that the net internal energy change of the system is zero. And even the process is adiabatic (dQ=0), it being expansion process contributes to increase in the entropy.
12) answer: (a) = It goes up.
Refrigerator is a device that transfers heat from inside a box to its surroundings. If we leave the door open, heat is just recycled from the room into the refrigerator, then back into the room. Also, we can’t design a fridge to be perfectly efficient (the 2nd law of thermodynamics guarantees this). So overall room temperature increases because of the heat of the motor that would be constantly running to move energy around in this loop.
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