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Homework Help: Thermodynamics: Change in Entropy

  1. Mar 11, 2008 #1
    1. The problem statement, all variables and given/known data

    A 50-ohm resistor carrying a constant current of 1 A is kept at a constant temperature for 27 deg. C by a stream of cooling water. In a time interval of 1s, (a) What is the change in entropy of the resistor? (b) What is the change in entropy of the universe?


    2. Relevant equations

    dS = dQ / T
    dQ = C dT


    3. The attempt at a solution

    For part a, I understand that the dQ of the resistor is zero because there is a constant temperature and current.

    For part b, I do not understand the relationship between resistance (50 ohm), and dQ. I arrive at the correct answer by plugging in 300K (27 deg C) in for T, and 50 ohm in for dQ, but I would like to understand the correct relationship. Any help?
     
  2. jcsd
  3. Mar 11, 2008 #2

    Mapes

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    Power generation (the amount of energy dissipated per second) is calculated as [itex]I^2R[/itex].
     
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