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Rusty wires and poor connections causing capacitative effect?

  1. Jul 24, 2013 #1
    Hi all!

    I am running an experiment in which I have rigged up a circuit to anodise aluminium foil. Running it with a constant voltage of ~40V I have found that rusty wires, poor connections (I am using alligator clips) and even using stackable banana plugs causes erratic (and high) currents which ruins my samples. With my limited knowledge in circuitry, all of these things might be modeled as resistors restricting the flow of electrons; however if they merely acted as resistors I cannot see why this should cause erratic current behaviour and shouldn't they reduce the current rather than increase it? Is it possible that they act as capacitors, "storing" the electrons and then releasing them sporadically causing current peaks?

    While I'm at it, would anyone have any idea about how to symbolically represent an electrolytic bath in a circuit schematic? (Would I represent the anode/electrolytic bath/cathode assembly as a capacitor in itself?)

    Thank you all in advance.
     
    Last edited: Jul 24, 2013
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  3. Jul 24, 2013 #2

    mfb

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    Even a perfect capacitor does not conduct "more" than a regular wire.
    There could be some inductance in the circuit - together with unreliable connections, this could lead to high voltages (and currents).
    As a work-around, you can connect a capacitor in parallel to the electrolytic bath.

    I would just invent a symbol (roughly representing two wires going into that bath).
     
  4. Jul 24, 2013 #3

    jim hardy

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    Wow would you post a link to the basics of what you are doing?
    I have some interest in amateur electrofinishing.

    40 volts sounds to me like an awful lot for a cell.
    Would you perhaps post asketch of your setup?


    to other question: I've seen electrolytic cells in very old equipment (1940's) represented as a dot and partial arc

    sorta " ° ) " but the dot more centered in arc

    perhaps surrounded by something resembling a test tube.
    Before Autocad draftsmen were more artistic.
     
  5. Jul 25, 2013 #4

    NascentOxygen

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    You're not mistaking the overshoot of a mechanical meter's needle as indicating a momentary overcurrent, are you?

    The current in a cell is greatly hindered by gas forming on the electrodes and causing an insulating layer (partially). This gas disperses with time, and is not present at startup. So if your connectors cause a high resistance, gas liberation decreases, then when good connection is re-established, there is a short higher current burst before gas buildup again hinders current flow.

    Rusty wires and poor connectors do exhibit capacitive effects at RF but not at the frequency you are using.

    Good luck with your explorations! :smile:
     
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