Parasitic capacitance and DC...?

Discussion in 'General Electronics Chat' started by tom66, Jun 24, 2009.

  1. tom66

    Thread Starter Senior Member

    May 9, 2009
    Capacitors block DC, and pass AC, right (according to -\frac {1} {2\pi f C})? So what about parasitic capacitance? All wires, especially breadboards, have a tiny amount of parasitic capacitance. So why don't most wires and breadboards block DC?

    Confused... :confused: I'm sure I'm making a mistake or something.
  2. steveb

    Senior Member

    Jul 3, 2008
    The parasitic capacitances looks like a capacitors from the wires to ground. This will not block DC along the main wires, but will short out high frequencies to ground. In acuality the high frequency equivalent circuit is hopelessly complicated and can not be effectively modeled using circuit theory alone. You really have wires which act like inductors and antennas, and then all these stray capacitors as well. But, this basic concept gives you an intuitive idea of what is happening.
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    Remember that the parasitic capacitance exists between conductors that are situated in proximity. A continuous conductor cannot exhibit capacitive signal blockage.