Appendix C Capacitors; How Capacitors Work - FIGnition FUZE Hardware Reference Manual

Appendix C Capacitors

Capacitors can be used to temporarily store charge and to smooth voltage regularities.
FiGnition uses them in both of these ways.
C.1 How Capacitors Work
Capacitors are basically metal plates with a large surface area separated by a thin insulat-
ing material. The large metal plates allow a relatively large surface area for a lot of elec-
trons and it's this that enables capacitors to store charge. It's even possible to build one
using drinks cans and waxed paper 12 (but I wouldn't recommend it, because of the danger
of suddenly discharging a relatively large amount of charge if you short-circuit it).
!
So the question is: if they have an insulating layer, how do they allow current to pass
through them? And the answer is that electrons don't pass through them; instead charge is
displaced (because electrons repel each other) and this explains their characteristics.
!
Imagine a 5v electrical power source is applied to one side of a capacitor (through a resis-
tor). Initially it starts off at 0v, but eventually electrons build up (they can't go anywhere)
until there's 5v on that side. Meanwhile, on the other side, the initial rush of charge repels
lots of electrons, but eventually there are few left at the right-hand plate to repel and so the
flow of charge there falls to a trickle.
12 DIY Capacitor image from http://rimstar.org/science_electronics_projects/make_electrolytic_capacitor.htm