Kirchhoff's Voltage Law

Discussion in 'Feedback and Suggestions' started by Red Bow Tie, Sep 9, 2013.

  1. Red Bow Tie

    Thread Starter New Member

    May 3, 2012
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    Here is the quote from volume 1 (DC) "In this series of textbooks, I have committed to using electron flow notation."
    Fine so I try my hand at the homework sheets for KVL and and questions 16 the answer is given according to conventional flow for current direction from left to right. (as least it has in brackets electron flow is right to left) Question 17 again has the answer given with respect to conventional flow.
    Of course, it doesn't matter much but until I noticed this distinction I couldn't come to the correct answer. So on question 17 would the correct answer for current direction be from top to bottom for the resistor if using electron flow?
    Would this mean that for electron flow voltage would rise going across a resistor?:confused:
    It seems easier to grasp a drop using conventional flow.
     
  2. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Are you having a problem because the "common point" between all the batteries is the ground symbol?
     
  3. WBahn

    Moderator

    Mar 31, 2012
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    It would be REALLY nice if you would post a link to the worksheet you are talking about. I hunted around and couldn't find one that seemed to match what you are talking about here.

    The owner of the site (and a few others) are big fans of electron flow. The problem is that they (and virtually everyone that tries to use it) do it in a way that mixes the notion of charge flow and charge carrier flow in subtle and unspoken ways. If done properly, the two are completely equivalent but you end up with lots of extra minus signs hanging around for electron flow because, for instance, if you connect a 2Ω resistor across a 12V battery you would have to say that you have a current of -6A flowing from negative to positive because "current" is a flow of charge, not charge carriers, and the electron has a negative charge.

    Far, far better to use conventional current from day one. But that's my opinion.
     
  4. adam555

    Active Member

    Aug 17, 2013
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    It doesn't really matter which direction you use; you should come to the same result. My electronics teacher always used electron flow, while I always use the opposite, and we both got the same results when doing Kirchoff exercises.

    For what you say the flow is confusing you towards the sign, but it has nothing to do with it. If a battery is in the same direction of the loop (whatever you chose) then it's positive; otherwise it's negative. And the sign of the resistors depend on the arrow you apply or are give to each wire in a node. So, if the current on the resistor is flowing out of the node, then it's negative; and if the current is flowing towards the node, then it's positive. Therefore, as you can see, the flow had nothing to do with it.
     
  5. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    The two questions mentioned have no resistors. Here is question 17, there are at least three other questions posing similar configurations. That would explain the OP's

    [​IMG]

    I'm not understanding the OP's intention when he mentions current flowing left, right, top, and bottom. Hopefully the OP will come back ...
     
  6. Red Bow Tie

    Thread Starter New Member

    May 3, 2012
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    Sorry for the confusion here is the link http://www.allaboutcircuits.com/worksheets/kvl.html
    However, I downloaded and saved the pdf version of the above and used that. Strangely enough on the html of the above link it is question #4. On the pdf it is question #17.
    Sorry for the confusion. Hope someone will see what I'm referring to.
     
  7. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Well, I would have never thought the html version and the pdf versions were different. I'm glad we are on the "same page" now.

    And yes I see what your talking about. stating conventional flow when the book stated the electron flow would be used.

    I'm going to report this to the admin's for inclusion in the "book problem" area. They will probably move the whole thread over there.
     
    Georacer likes this.
  8. Red Bow Tie

    Thread Starter New Member

    May 3, 2012
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    Thanks Joe for continuing to follow this thread. As well, question #16 on the pdf is #20 on the html. I haven't checked any other ones yet and the only reason I checked these ones is because my answer using electron flow was incorrect.
    Now on #4 (#17 pdf) does this mean the correct answer using electron flow is from top to bottom?
    Also, using electron flow do we look for a voltage rise across a resistor (-1.87v) being "higher" than -5.04V for the direction of current? It seems harder to think of a resistor raising voltage to ground (using electron flow) than dropping voltage to ground using conventional flow or is my thinking completely off base?
    If so could you give me a hint where my thinking goes wrong?
     
  9. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The online versions of the eBook are more frequently updated.
    The PDF's are a kind of snapshot of a certain date.
    The online version is maintained by Dennis ( Dcrunkilton )

    Bertus
     
  10. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Note, please don't follow this confused and incorrect description of Kirchoff's Laws.
     
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