Capacitive coupling

Hi so I've been doing some research on capacitive coupling and I just wanted to see people's thoughts on my understanding as the stuff out there is a little difficult to follow and doesn't really provide much help. 

So from my understanding capacitive coupling occurs between an energized conductor and a non energized conductor due to the difference in potential difference.  From what I can see this is very similar to mutual inductance I am assuming the key difference is that mutual inductance works by inducing a current where as capacitive coupling works by transferring a voltage. 

Is this correct 

Thank you in advance 

Sam 

Parents
  • sort of.  Any two pieces of metal have some capacitance between them, but of course it only matters when there is an ac voltage between them to drive the flow of the displacement current.

    The thing to realise is that capacitance falls with distance and rises with area facing the other 'plate' and in cables is tens to hundreds of pF (picofarads - 1E-12 Farad) per metre - large capacitors use a swiss-roll construction of rolls of foil and thin plastic to get two conductors very close with a large area facing each other - by being a hundred times closer and areas of many square metres, capacitors a million times larger (in the microfarads to tens of microfarads range) are then quite possible and handy sized,

    If you  are in the habit of using the 'juice' mental model of electricity as being fluid like in pipes in place of wires, then the analogue of a capacitor would a rubbery membrane stretched across the area of the pipe - allowing changes in pressure to be transmitted but not a DC flow. Inductance however is more like some coupling between a propeller in the moving liquid and a heavy flywheel - where it is the moving of the charges that is important, rather than the pressure.

    Happy to discuss further and fill in any areas you feel are patchy for you.

    Mike

  • So is it the change in current caused by the AC wave form which allows the current flow through the capacitor due to the constant charge and discharge they might not be the right words but I think it shows my point. 

    What do you mean by the area facing the other plate is that referring to the size of the opposite plate or for example a cable? 

    So having an inductor in a circuit is basically like having a large form of resistance does this work in a similar principle as a capacitor where it reacts to the change in alternating current. 

    Thank you for taking the time to reply it's definitely made things that bit clearer

    Sam 

Reply
  • So is it the change in current caused by the AC wave form which allows the current flow through the capacitor due to the constant charge and discharge they might not be the right words but I think it shows my point. 

    What do you mean by the area facing the other plate is that referring to the size of the opposite plate or for example a cable? 

    So having an inductor in a circuit is basically like having a large form of resistance does this work in a similar principle as a capacitor where it reacts to the change in alternating current. 

    Thank you for taking the time to reply it's definitely made things that bit clearer

    Sam 

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