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Homework Help: What is the maximum power rating of a kettle

  1. Nov 6, 2005 #1
    Hey, i got a circuit question, and i'm not sure if i did it right, and was wondering if anyone could show me how to do it

    A 750W microwave oven is plugged into an outlet and turned on. All three lights are on. What is the maximum power rating of a kettle that could be operated in the other outlet without burning out the fuse.

    a) 1.80 x 10^3W
    b) 7.50 x 10^2W
    c) 1.05 x 10^3W
    d) 9.50 x 10^2W

    What i did is, for each awnser i took the power reading and divided it by the total voltage, since P = IV P/V = I, i found out that the 1800W one produced a current of 15A and that was my awnser, but my other friends got 1500Wats as the

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  2. jcsd
  3. Nov 6, 2005 #2


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    Staff Emeritus
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    Perhaps you need to consider the load presented by the microwave and the lightbulbs?
  4. Nov 6, 2005 #3
    if we consider the bulbs then it be 300W + 750Wats added which is 1.05 x 10^3 but that doesnt equal the total power it can reach.
  5. Nov 6, 2005 #4


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    Homework Helper

    that's right, how much reserve power remains for the tea-kettle?
  6. Nov 6, 2005 #5
    hmm Okay So i have 1050Wats/120V = 8.75 A so then 750/120 = 6.25 together they equal 15, so then would it be 750? but i'm not counting the inital current of 2.5A so i'm doin somethin wrong.
  7. Nov 6, 2005 #6


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    what initial current of 2.5 A? Everything adds up to 1800 Watts.
  8. Nov 6, 2005 #7
    i dont think it is 1800wats, cuz that ALONE = 15A, and we still havent included the 750W microwave + the 300Wats of lightbulbs
  9. Nov 6, 2005 #8


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    Homework Helper

    Pay attention!
    EVERYTHING adds up to 1800 Watts.
    1050 Watts already on, + 750 Watts kettle.
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