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Homework Help: Light bulb circuit

  1. Jun 12, 2012 #1
    A DC circuit has resistances of 10Ω, 12Ω, and 10Ω respectively. Also has 2 light bulbs with identical tungsten (resistivity = 5.6* 10^-8) filament bulbs with filament thickness of 12um and length of 1.2cm. The source is a 12V.

    what is the power loss over the first light bulb?

    I am not entirely sure which equations to use how ever the ones which i thought to use are:
    P=V^2 / R
    I am really stuck and dont know how to find the acual power loss. I think my main issue is gather the correct information and implimenting it in the right situation.

    I have attempted to find the total, R1+R2+R3= 32Ω
    And then i have divided each by the source 12... 2.66A
    Can someone please direct me in the right way...? I am gettin quiet frustrated with it!!
  2. jcsd
  3. Jun 12, 2012 #2


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    Homework Helper

    hi lofty28! :smile:

    yes, that's the right method, find the current first, and then find the power through the bulb with that current

    (but you'll need to add the resistances of the two bulbs, and add them, before finding the current :wink:)
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