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Homework Help: Brightness of Light Bulbs Ranking Task

  1. Jun 15, 2010 #1
    1. The problem statement, all variables and given/known data
    Consider a circuit containing five identical light bulbs and an ideal battery. Assume that the resistance of each light bulb remains constant. Rank the bulbs (A through E) based on their brightness.
    Rank from brightest to dimmest. To rank items as equivalent, overlap them.

    2. Relevant equations

    V=IR, junction law and loop law

    3. The attempt at a solution

    i use that fact that more resistance means that less current flow by looking at the pic the current in A&B are the same, but the current in C is greater than in D&E where current in D&E are same b/c of series. there for conclude that C>(A=B)>(D=E)

    can any 1 tell me if this is right plz!
  2. jcsd
  3. Jun 15, 2010 #2
    its right
  4. Jul 6, 2010 #3
    If anyone didn't mind me asking, I was wondering WHY Bulb C has less resistance compared to Bulb A or B?
  5. Apr 15, 2011 #4
    It doesn't have less resistance, all resistances are the same. It has more voltage because the equivalent resistance of RcRdRe is greater than that of RaRb. If you link brightness to power (P=I*V) and Rab has the same current as Rcde, then because the voltage is higher Rc has more power.
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