University of California, San Diego
Physics 1b - Thermal Physics & Electromagnetism

H. E. Smith   Spring 2000

Physics 1B - Tutorial #3

  1. All the processes shown below have the same inital pressure (2 atm = 2 x 105Pa) and volume (100 cm3) and end at the same values of pressure (2 atm) and volume (300 cm3). Which diagrams represent the same amount of work done by the system?

    W = PdV = Area under the PV curve.

  2. Starting from the point shown sketch

  3. For each case below describe whether the diagram represents a possible (i.e. does not violate the Laws of Thermodynamics) heat engine or refrigerator. If not describe what is wrong.

  4. On a warm day your roommate suggests that you leave the refrigerator door open to "cool this place down." After a while with the fridge door open will the room be cooler, the same or warmer? Explain.

    The initial blast of cold air may feel good, but close the door fast! This will heat up the room further. The energy that you must use to operate the refrigerator is transformed into heat and exhausted into the room, so more heat is introduced into the room than is removed. Note that an air conditioner exhausts the heat to the outdoors. OK

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Gene Smith

Last modified: Thurs., 20 Apr 2000