Parallel/series circuit

Discussion in 'Homework Help' started by Niles, Jan 18, 2009.

  1. Niles

    Thread Starter Active Member

    Nov 23, 2008
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    Hi all.

    Please take a look at the attached circuit.

    Am I correct when I say that resistor 1 and 2 are in parallel, and these are in series with resistor 5, which are in series with the parallel resistors 3 and 4?

    I hope you understand me. Thanks in advance.

    Sincerely,
    Niles.
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    No you are not correct. Two resistors to be in parallel must have the same voltage across them. Do these resistors have the same voltage? No!
     
  3. Niles

    Thread Starter Active Member

    Nov 23, 2008
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    So when using Kirchhoffs law on each resistor, the same terms must appear on both sides for the resistors to be in parallel?

    Thanks for responding quickly.
     
  4. Niles

    Thread Starter Active Member

    Nov 23, 2008
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    Is this a very good definition to use?

    "A parallel circuit is one where the electrical components are connected between two points with one of the two ends of each component connected to each point."
     
  5. mik3

    Senior Member

    Feb 4, 2008
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    I am sorry I didn't understand your question. Which Kirchhoff's rules?
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    Yes you can say it but have a look here too:

    http://www.allaboutcircuits.com/vol_1/chpt_5/1.html
     
  7. Niles

    Thread Starter Active Member

    Nov 23, 2008
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    Don't be sorry, I asked it in a very confusing way. Perhaps I should have asked: "How did you see that the voltage across resistor 1 and 2 are not the same?"

    Thanks for the link. I'll check it out.
     
  8. hgmjr

    Moderator

    Jan 28, 2005
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    Here is an ebook link to the section on wheatstone bridge. This solution shows the application of mesh analysis rather than Kirchhoff's Voltage or Current Law. It may still prove helpful.

    hgmjr
     
  9. mik3

    Senior Member

    Feb 4, 2008
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    Because R5 has a voltage drop across it or because the bottom terminals of resistor 1 and 2 are not connected together with a wire but with a resistor.
     
  10. Niles

    Thread Starter Active Member

    Nov 23, 2008
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    Ahh, so you used Kirchhoffs loop rule on the loop containing resistor 1, 2 and 5. Very clever.

    So when I am in doubt, I should use this strategy, and when the voltage across the two components are equal (i.e. there is no 3. contribution like in this case), I can conclude they are in parallel?
     
  11. hgmjr

    Moderator

    Jan 28, 2005
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    I believe that is a safe assumption.

    hgmjr
     
  12. Niles

    Thread Starter Active Member

    Nov 23, 2008
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    I was more worried if my method of finding out when the voltage drop across the two components is equal is correct; can I just use Kirchhoffs loop rule for the loop containing the two components?

    Thanks to both of you for participating.
     
  13. hgmjr

    Moderator

    Jan 28, 2005
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    When dealing with a loop, you must take into account all resistors that exist in the loop.

    hgmjr
     
  14. Niles

    Thread Starter Active Member

    Nov 23, 2008
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    0
    Thanks to both of you.
     
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