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What is Work and Heat

  1. Dec 3, 2015 #1
    1. The problem statement, all variables and given/known data
    After looking through several websites, everyone seems to have their own interpertation of this. My physics textbook says that Work is the change in energy, some people online say that Work is a form of energy and Heat can be changed into work and vice versa. My chemistry book says that Heat is the transfer of energy from a hot object to cold object as a result of the temp. difference between them. It also ssays Work is done as a result of motion against an opposing force. Some others online say that Energy is transfered to the motion of atoms and molecules. Others say that Work is energy transfered to motion of objects. HELP

    2. Relevant equations


    3. The attempt at a solution
     
  2. jcsd
  3. Dec 3, 2015 #2
    I would like to sort of settle on two definitions. I found this one in another physics place. Work is the energy transferd to or from an object by means of a force acting on the object. Is this correct?
     
  4. Dec 3, 2015 #3
    When you had freshman physics, what was the definition of work?
     
  5. Dec 3, 2015 #4
    Every year with different teachers etc. everyone changes their definitions. I think I learned this first, Work is the ability to transfer energy or something like that.
     
  6. Dec 3, 2015 #5
    And this is the definition of work they taught you in freshman physics?
     
  7. Dec 3, 2015 #6
    Don't exactly know what freshman physics is. Im assuming thats American education system. Im in Europe.
     
  8. Dec 3, 2015 #7
    That was probably the earliest definition I could recall.
     
  9. Dec 3, 2015 #8
    So you never heard of work equals force times distance?
     
  10. Dec 3, 2015 #9
    Yes I have. W=Fd. They usually tell us both equation and worded definitions
     
  11. Dec 3, 2015 #10
    OK. So we are on the same page. The work is a macroscopic quantity. In thermodynamics, it is also force times distance. In the case of thermodynamics, we often get the work as W = PΔV, where p is the pressure (force per unit area) and ΔV is the change in volume. Note that pressure is force divided by area, while change in volume is displacement time area. So, it's really the same thing.

    Now for heat. Do you remember from freshman physics when you had one end of a rod at a high temperature and the other end of the rod at a low temperature? We said that the rate of heat flow was equal to the cross sectional area times the thermal conductivity k times the temperature difference divided by the length of the rod. We called this the rate of heat conduction. This is the same kind of thing that happens thermodynamics when we talk about heat flow.

    Chet
     
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