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Homework Help: A question i just cant get

  1. Sep 16, 2008 #1
    hi all i have a question to do but i cant seem to get my head round it and i was hoping some of you might be able to explain it better so here it is:
    "the coiled filaments in a main lamp and a car head lamp are made of the same material and have the same length. Use the info. below to calculate the ratio:
    cross sectional area of the mains lamp filament/cross sectional area of the headlamp filament

    Mains lamp: 230V; 100W Car headlamp;12V; 36W

    Many thanks
  2. jcsd
  3. Sep 16, 2008 #2


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    Homework Helper

    Your power is W = I2R

    What do you suppose are the differences in current between the 2?
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