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Homework Help: Resistance of Light Bulbs in Parallel

  1. Apr 22, 2015 #1
    1. The problem statement, all variables and given/known data
    Eight lights are connected in parallel to a 110-V source by two long leads of total resistance 1.6 Ω.

    a. If 302 mA flows through each bulb, what is the resistance of each?

    b. What percent of the total power is wasted in the leads?

    2. Relevant equations

    R. The attempt at a solution

    I found the total resistance to be 45.5298 V but when plugging that in to find the resistance of each bulb, I can't seem to get to the right answer. What am I missing here?
  2. jcsd
  3. Apr 22, 2015 #2


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    It can be calculated in many ways (how did you do it?).

    1) You can find the resistance in one bulb, (Rbulb=V/Ibulb), after that finding Rtotal in 8 bulbs in parallel.
    2) You can find the total power, after that using Ptotal=V2/Rtotal
    3) You can find the total current, after that using Rtotal=V/Itotal
    Last edited: Apr 22, 2015
  4. Apr 22, 2015 #3
  5. Apr 22, 2015 #4


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    Gold Member

    The voltage drop for each bulb is 110V (bulbs are in parallel). Your Rbulb is correct, and so is your Rtotal in #1.

    But then I cannot understand this in #1:

    What's your problem here?
    Last edited: Apr 22, 2015
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