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About thermal energy

  1. Nov 7, 2007 #1
    One question ask:

    "Which of the following statements is true? Select the correct answer."

    a.The quantity of thermal energy exchanged by two bodies in contact is directly proportional to the difference in their temperatures.
    b.You only need to know the amount of thermal energy a body contains to calculate its temperature.
    c.The temperature of a body is directly proportional to the amount of work the body has performed.
    d.The quantity of thermal energy exchanged by two bodies in contact is inversely proportional to the difference in their temperatures.
    e.Different amounts of thermal energy are transferred between two bodies in contact if different temperature scales are used to measure the temperature difference between the bodies.

    Answer is a.

    The other question ask:

    6)If an object feels cold to the touch, the only statement that you can make that must be correct is that:
    A. The object has a smaller coefficient of thermal conductivity than your hand.
    B. The volume of the object will increase while it is in contact with your hand.
    C. The object contains less thermal energy than your hand.
    D. The object is at a lower temperature than your hand.

    Answer is D.

    In this two question, both sentences are wrong
    "You only need to know the amount of thermal energy a body contains to calculate its temperature"
    "The object contains less thermal energy than your hand"

    May I know
    Why thermal energy can't determine temperature?
    Why the above two statements are wrong?
     
  2. jcsd
  3. Nov 7, 2007 #2
    Temperature is an average of the kinetic energy isn't it? Thermal energy is the total. So you could have a really big "cold" object and it would have more energy then say a small "hot" object. But the average energy of the hot object would be greater than the average of the cold object.

    "You only need to know the amount of thermal energy a body contains to calculate its temperature"
    -You need to know something about the size of the objects and the particles that made it up?

    "The object contains less thermal energy than your hand"
    -It could be a large cold object, so it could have a greater amount of energy but over a larger area, so it's just the temperature that is lower.

    I've only studied thermodynamics a little, but I think that's sorta right...
     
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