Electronics Basics - Arduino Sketches: Tools and Techniques for Programming Wizardry - page 53

Figure 3-6: A resistor used to power an LED
Capacitors
Where resistors are designed to resist electric current, capacitors are designed
to store small amounts of electric energy.
Capacitors are composed of two parallel sheets of conductor separated by a
thin nonconductor, which could be made from a number of materials, such as
paper, mica, ceramic, plastic, and sometimes even air. When connected to electric
potential, electrons are attracted into the capacitor and released when the outside
voltage drops. A capacitor is, essentially, a small (and weak) rechargeable battery.
Capacitors come in many shapes and sizes and can be some of the smallest
components available to the biggest, capable of dwari ng entire battery packs.
Have you ever taken apart an electronic device and seen large, cylindrical com-
ponents, normally in blue or black plastic? Chances are those are electrolytic
capacitors, and you probably have not seen the biggest available.
WARNING Some capacitors can be connected any way in a circuit; others must
be placed in a certain way. Electrolytic capacitors especially have a polarity, and this
must be respected. Failure to correctly polarize electrolytic capacitors can result in
catastrophic failure; the component will leak or explode, potentially damaging the
rest of your circuit. Don't try this at home!