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Homework Help: Energy balance

  1. Mar 26, 2013 #1
    For the following question, the solution manual sets du/dt (change of internal energy) = 0. Moreover, it also set the change of total entropy to zero. Why is that?

    An electric motor under steady load draws 9.7 amperes at 110 volts; it delivers 0.93 kW of mechanical energy. The temperature of the surroundings is 300 K. What is the total rate of entropy generation Sg ? What is its origin ?
    Last edited: Mar 26, 2013
  2. jcsd
  3. Mar 27, 2013 #2


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    Staff: Mentor

    Energy is conserved. I would expect some entropy generation (the problem statement even asks for its amount!), however.
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