More Than You Ever Wanted to Know About Electrical Engineering: Parasitic Capacitance and Crosstalk
We know that a capacitor is simply two conductors spaced closely together with some nonconductive material between them. If you think this sounds like a really common situation, you’d be right - it’s very easy to accidentally create an “invisible” capacitor in a circuit. Two wires next to each other meet the definition of a capacitor, after all - there’s two conductors separated by a nonconductive material.
The capacitance you unintentionally produce in a situation like this is called a parasitic capacitance. In a lot of cases, it’s a negligible effect. The wires (or whatever conductors you’re concerned with) are far enough apart so there’s very little capacitance occurring, or you’re operating in a regime where capacitative effects have relatively little impact on what you’re trying to do. However, there are definitely situations in which parasitic capacitance absolutely wreck you.
Let’s look at a couple of wires running right next to each other.