Circuits: Household Circuit

  1. 1. The problem statement, all variables and given/known data
    What current would flow in an ordinary 115 V household circuit, if a 1385 W hair drier and a 625 W microwave oven were operating simultaneously on this line?
    Answer: 17.48 A

    How much current would the hair drier and microwave from the previous question draw, if they were connected to the 115 V line in series?
    Answer: Unknown

    2. Relevant equations
    P=IV, V=IR


    3. The attempt at a solution
    I'm looking for an answer to the second question. Aren't the first and second questions the same? I can't see the difference...
     
  2. jcsd
  3. mgb_phys

    mgb_phys 8,952
    Science Advisor
    Homework Helper

    What a dumb question!
    What they want you do is calcualte the restance of them assuming the powers given above, then calcualte the series resitance and use that with 115v to get a power.
     
  4. thanks, but you don't have to be so mean! sheesh! We all make stupid mistakes
     
  5. I think he was referring the question in your text, not your question about the question.
     
  6. mgb_phys

    mgb_phys 8,952
    Science Advisor
    Homework Helper

    Sorry I meant it was a stupid question in the book - you don't connect 115V ac appliances like that. I would have been tempted to say 0A because the microwave wouldn't turn on!

    It's the sort of thing that puts people off physics - they think it's all just trick questions, when you are supposed to ignore friction here or assume the weight of the rope doesn't matter there.
     
    Last edited: Feb 14, 2008
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