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Identical bulbs, rank by brightness

  1. Apr 9, 2016 #1
    1. The problem statement, all variables and given/known data
    Which bulb(s) will have the higher light intensity?


    2. Relevant equations
    Resistors:
    Connection in series: same current
    Connection in parallel: same delta V

    3. The attempt at a solution
    A and C are in series. They'll be equally bright. B is not connected to the negative terminal of the battery. no current will pass through it. Hence A=B>C
     
  2. jcsd
  3. Apr 9, 2016 #2
    tmp_27523-20160409_2030471282769602.jpg
     
  4. Apr 9, 2016 #3

    billy_joule

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    I agree with your answer and reasoning.
     
  5. Apr 9, 2016 #4

    phinds

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    huh ?
     
  6. Apr 9, 2016 #5
    Incorrect??
     
  7. Apr 9, 2016 #6

    phinds

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    well, what do you mean by it? What it says to me is very literal, A equals B and either both are greater than C or at least B is greater than C. I don't see how you get that from what's going on. Do you mean something else?
     
  8. Apr 9, 2016 #7
    I mean that A and B are equally bright and that both are brighter than C
     
  9. Apr 9, 2016 #8

    phinds

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    Yes, that's what I thought. Is that really what's happening?
     
  10. Apr 9, 2016 #9
    Sorry, I was confused. I meant A=C>B. Also, is there any current passing through B at all?
     
  11. Apr 9, 2016 #10

    phinds

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    Yes, that makes sense.

    what do you think?
     
  12. Apr 9, 2016 #11

    I think there's no current passing through B at all. My reasoning: why would the electrons go through path with a resistor that does not lead to the negative terminal of the battery when they have the choice to take a resistless (ideally) path that leads to the negative terminal of the battery.
     
  13. Apr 10, 2016 #12

    NascentOxygen

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    I don't understand this. Can you explain?
     
  14. Apr 10, 2016 #13

    cnh1995

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    Your answer is correct. Have you studied what an "open circuit" is?
     
  15. Apr 10, 2016 #14
    Not yet, but I am curious. I'll look it up. Is it when there is a gap somewhere on the circuit so the current pass? What is it useful for?
     
  16. Apr 10, 2016 #15

    cnh1995

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    It is the technical term for a "gap" in the circuit, so current can't flow through it.
    A circuit needs to be closed for the flow of current. Here, no current flows through bulb B since there's no closed path.
     
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