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Charge flow in simple circuits

  1. May 12, 2017 #1
    1. The problem statement, all variables and given/known data

    upload_2017-5-12_12-46-12.png
    3. The attempt at a solution

    Top left: No charge flowing through circuit b/c switch is open, not closed.
    Top right: No charge flowing through circuit b/c circuit does not connect positive and negative terminals
    Bottom left: Charge flows through circuit b/c closed loop between + and - terminal.
    Bottom right: No charge can flow through since negative terminal cannot be directly connected to another negative terminal.

    Please let me know if these answers are correct and how I can make them better. Thank you!
     
  2. jcsd
  3. May 12, 2017 #2

    phinds

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    RIght answer for the wrong reason. It's perfectly acceptable to connect negative terminals.
     
  4. May 12, 2017 #3
    Thank you so much for you response phinds! :)

    I don't get this. But I would say it as 2 positive terminals are making up the circuit, and they not sending any electrons through the circuit essentially. The electrons are all concentrated at the wire connecting the 2 negative terminals.
     
  5. May 12, 2017 #4

    phinds

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    No, that is not correct. Everything you see is part of the circuit, it's just a question of whether or not current flows through the various parts (it doesn't).What is the potential on each side of the bulb?
     
  6. May 12, 2017 #5
    The potential on the positive side is maximum. The potential on the negative side is 0?
     
  7. May 12, 2017 #6

    phinds

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    I have no idea what your reference is. what do you mean "the negative side"? I'm not asking you about the battery, I'm asking you about the bulb. Please read my question again.
     
  8. May 12, 2017 #7
    Here is what I mean:

    upload_2017-5-12_13-19-5.png
     
  9. May 12, 2017 #8

    phinds

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  10. May 12, 2017 #9
    I think the potential on each side of the bulb is maximum?
     
  11. May 12, 2017 #10

    phinds

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    Yes, but it's irrelevant whether or not it is maximum, minimum, or anywhere in between. Focus on why no current flows.
     
  12. May 12, 2017 #11
    There is no potential difference across the bulb so no current can flow. The potential is the same everywhere on the right side of the circuit between the 2 positive terminals?
     
  13. May 12, 2017 #12

    phinds

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    Exactly.
     
  14. May 12, 2017 #13
    Thank you so much phinds :D I get it now.
     
  15. May 12, 2017 #14

    phinds

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    Now let me pose another question to extend the problem, and your understanding.

    Those are ideal batteries. Now let's consider real-world batteries which have internal resistance. Suppose one of the batteries has a .01 ohm resistor in series with its positive terminal and the other battery has a .012 ohm resistor in series with its positive terminal. Does the answer change?
     
  16. May 12, 2017 #15
    Wow great. :) I will try to solve this after my classes today. Thank you.
     
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