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Circuit schematics: Equivalent Representations of circuits

  1. Mar 9, 2013 #1
    Attached is a schematic of interest. Assume same voltage source and capacitance for each capacitor in each circuit.

    Correct me if I'm wrong, it appears all circuitry comprises two basic types of connection: series and parallel. I'm trying to figure out an approach to determining whether a component (or group of components) is in parallel or series with another component (or group of components) in different (but equivalent) schematic representations.

    My approach involves analyzing the possible paths at a junction and making sure that in another equivalent diagram, the connections are preserved e.g., in the upper circuit, the connection that goes through path 1, 2, and 4 is preserved in the lower circuit where the connection goes through 5,6,8 in the same manner.

    How's my approach? Are there any other approaches?

    Attached Files:

  2. jcsd
  3. Mar 10, 2013 #2
    I don't know what are you trying to ask here.
    Well yes basically there are two main connection types parallel and series but what is that in your schematic?
    What is the question with that schematic as it is basically two parallel capacitors connected with two other parallel capacitors?
    Normally the way you have drawn the schematic it would look like just one cap in series with another cap , there is no need for two parallel capacitors which are then connected together and connected to another set of two capacitors.
    The only reason i would use capacitors in a schematic like yours in parallel in when i would need huge capacitance and one would not be enough then I would put another one in parallel.

    By the way those two schematics are totally similar I don't know why you repeated them do you think there is a difference between them?
  4. Mar 10, 2013 #3
    Hi, sorry for the confusion.

    No, there isn't a difference between the two schematic. Obviously, they're different representations of the same connection between two parallel connected capacitors that are connected in series, as you've mentioned. However, I'm not interested in simplifying the circuit as much as I'm interested in the connections between those components.

    Suppose we had other discrete components that are not the same. One schematic representation (call Rep1 the upper schematic and Rep2 the lower schematic) is more clear to read than the other. My question is: how do you prove the schematics are equivalent -- that current won't flow differently in one schematic than in the other? Notice that I care more about the way the components are connected than what the discrete components are.

    I propose to look at the connections between the components, particularly the capacitor plates of both Rep1 and Rep2 not connected to Vcc or Ground (so the central plates). If we take any one plate, as long as we can draw a continuous line from this plate to another plate, in both Rep1 and Rep2, than the schematic is equivalent. Are there any counterexamples to my method? Essentially, I'm trying to figure out how to simplify "redundant wires" e.g., redundant wires in the attached diagram. A question for the appended diagram is: where do I place the two rightmost capacitors so they are equivalent in representation to Rep1 and Rep2?

    Attached Files:

  5. Mar 11, 2013 #4
    I also have to say I'm not following what you're trying to do. You can solve for the equivalent capacitance by using the basic formulas for combining capacitors in parallel and in series.
  6. Mar 11, 2013 #5
    in the lower schematic those last two capacitors looking from ground side are totally useless because you shunted them with a wire that is parallel to them so their use just cancels out.

    Hey I really can't understand what are you trying to make?
    If you want to know if capacitors can be put in parallel or series they can be put however you like as long as that works for the specific circuit that you or someone else is building.
    Things should be as simple as possible but not simpler said Einstein and I agree if you can have one capacitor in series with another one then why put two parallel capacitors series with another two?
    Useless, unless you have a application that need a lot of capacitance and one capacitor rating is not enough.

    If you want to know were you put those wires so that the two schematic look the same well it's like drawing too a like people or similar just take the unnecessary things out like those wires that are totally useless in your lower circuit just take them out.

    But still I don't understand what are you trying to do here? Can you be more specific is this for school for hobby for a friend for what is it?
    What exactly are you trying to learn ?
    There are multiple books on simple circuits and complicated ones you can even read some of them in internet for free , books like audio power amplifier designbooks and so on.I suggest that you get one of those and try to replicate and understand the most simple desgins and then see how they work get familiar with the stuff and then you will understand yourself.
    If you need give an email or let me know if you want a PM I can send you some simple circuits that work that i have built myself.
  7. Mar 11, 2013 #6


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    Are these capacitors in parallel or series? neither? both? :-)


    There is no right answer. However in some situations it's better to think of them in parallel and in other series.

    What do you make of the diode and capacitor ladder network in this circuit..


    What about D4 as an example. Is that in series or parallel with anything?

    You can't allways treat components as being in series or parallel.
  8. Mar 11, 2013 #7


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    I spy the dreaded Classification Monster lurking here. Series and Parallel are just convenient names which we give to arrangements of components - particularly when it's 'obvious' what to call them.
    What is the point of asking whether those two capacitors are in series or parallel? If you connect across them, then they will appear in parallel but if you break into the circuit and look that way, they will appear in series.
    That diode D7 has current through it as a result of the volts across it. Who cares what you call it?
    You can just give yourself sleepless nights over questions like this and they are just not necessary. This is not the way in to understanding electronics.
  9. Mar 11, 2013 #8


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