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Wire and resistor in parallel

  1. Jan 19, 2015 #1
    • Member warned about lack of template
    If a "normal" looking wire and a resistor are in parallel on a simple circuit diagram, will any current pass through the resistor?
     
  2. jcsd
  3. Jan 19, 2015 #2

    Bystander

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    Yes, E/R. It's going to be a very small current since the voltage drop across the wire is going to be very small.
     
  4. Jan 19, 2015 #3
    For the purpose of the problem, do you think the current through the resistor would be considered negligible?
     
  5. Jan 19, 2015 #4

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    You haven't included a problem statement? I've no way of knowing.
     
  6. Jan 19, 2015 #5
    8zmur8.png
     
  7. Jan 19, 2015 #6

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    No difference. You'll want to recalculate R1 it that's actually a "140" I'm reading. As far as the short circuit around R2 for this problem, yes, call it zero.
     
  8. Jan 19, 2015 #7
    I'm attempting this by finding the voltage drops at the two known resistors. However, R2 has a voltage drop of .02 A (1,000 Ω) = 20 V. How is this possible, as the battery is only 5 V?
     
  9. Jan 19, 2015 #8

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    The wire has a nearly zero resistance. It is in parallel with R2. What is the resistance of two resistors in parallel? When one is the next thing to zero?
     
  10. Jan 19, 2015 #9
    Ooo. I thought we'd established that the current through the wire was nearly 0.

    I'd say that the resistance would be very small.
     
  11. Jan 19, 2015 #10

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    Yes. Sorry, I thought you'd picked up that the wire is carrying nearly all the current, and that the current through the resistor would be just whatever it carries for the very small voltage drop across that length of wire.
     
  12. Jan 19, 2015 #11
    I got 130 Ω after solving the following equation for R1:
    3.5 V = .02 A (120 Ω + R1)
     
  13. Jan 19, 2015 #12

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    That's good.
     
  14. Jan 19, 2015 #13
    Awesome! Thanks for the help!
     
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