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Homework Help: Refrigerator and its light bulb

  1. Dec 14, 2009 #1
    The interior lighting of the refrigerators is provided by
    incandescent lamps whose switches are actuated by the opening of the
    refrigerator door. Consider a refrigerator whose 30-W lightbulb
    remains on continuously as a result of a malfunction of the switch. If
    the refrigerator has a COP of 1.4 and the cost of electricity is Rp
    1200/kWh, determine the increase in the energy consumption of the
    refrigerator and its cost per month (1 month = 30 days) if the switch
    is not fixed. Assuming the refrigerator is opened 50 times a day for
    an average of 30 s.




    COP= QL/(QH-QL)
    COP= Qin/Win



    Please help me for this. thanks a lot!
     
  2. jcsd
  3. Dec 14, 2009 #2

    Andrew Mason

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    You will have to show us your thoughts on this. To start, what is the rate of work that the refrigerator motor has to do to remove 30 W of heat?

    AM
     
  4. Dec 15, 2009 #3
    When you've worked out the energy required for the refrigerator to pump out the heat, don't forget to add the original 30W of electricity consumed by the bulb to the total. It's all got to be paid for!
     
    Last edited: Dec 15, 2009
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