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How do I know what's in series and what's in parallel in this circuit?

  1. Sep 27, 2014 #1
    I've found many methods on how to know whether resistances are in parallel or in series but I don't know how to apply any of them on this one tmp_27980-New Doc 2_1-349246184.jpg tmp_27980-New Doc 2_1-349246184.jpg
     
  2. jcsd
  3. Sep 27, 2014 #2

    sophiecentaur

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    Hi and welcome to PF.
    I think that this is an example of a circuit in which the simple classification of series or parallel doesn't help when trying to analyse it. You can apply Kirchoff's laws to solve such problems and they do not use names like series or parallel - they just use nodes and loops. (I don't know whether or not you have come across Mr K, yet but he can be very useful)
    This link shows how such arrays can be analysed, using the transforms provided in it - so you don't need to use Kirchoff for those straightforward arrangements..
     
  4. Sep 27, 2014 #3
    I notice that R2 through R5 forms a wheatstone bridge circuit with R1 in parallel with it. The unmarked resistor is where the meter or null indicator would normally go.
     
  5. Sep 28, 2014 #4

    NascentOxygen

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    As has been stated, there is series, there is parallel, and then there is other. :)

    The arrangement shown becomes very easy to analyze if you are told that R4=R5 and R2=R3. Under those conditions you can completely overlook the resistor which when labelling you already seem to have overlooked. :w

    It is a favourite of examiners to use a 5 resistor arrangement like this on a test paper, and give it that simplifying condition without highlighting having done so, therefore it's in your interest to always be alert to that.
     
    Last edited: Sep 28, 2014
  6. Sep 28, 2014 #5
    I forgot to mention that it said that all resistors have the same resistance
     
  7. Sep 28, 2014 #6
    Can't add much to this discussion except to confirm that there is "other". :)
     
  8. Sep 28, 2014 #7

    NascentOxygen

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    Okay! http://deephousepage.com/smilies/thumb.gif [Broken]
     
    Last edited by a moderator: May 7, 2017
  9. Sep 29, 2014 #8
    Hi,
    It looks to me like you have a Y-arrangement inside a Delta-arrangement. You could tackle this by say, converting the Y to a Delta and then you get two Deltas 'on top of each other', i.e. in parallel.

    Here are the details on Y-Delta transforms:
    http://en.wikipedia.org/wiki/Y-Δ_transform
     
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