Parasitic capacitance and DC...?

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

1. tom66 Thread Starter Senior Member

May 9, 2009
2,613
218
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... I'm sure I'm making a mistake or something.

2. steveb Senior Member

Jul 3, 2008
2,433
469
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
15,815
293
Remember that the parasitic capacitance exists between conductors that are situated in proximity. A continuous conductor cannot exhibit capacitive signal blockage.