Circuitbuilding Do-It-Yourself For Dummies®

Chapter BC2. Capacitor Types

Topics Covered in This Chapter

• How a capacitor works

• Building your own capacitor

• Choosing a capacitor type

As you learn how to build circuits, you will undoubtedly work more and more with capacitors. This bonus chapter gives you the rundown on how capacitors work, how to build your own, and what to look for when picking a capacitor.

Meet the Capacitors

A capacitor is just a pair of conducting plates (electrodes) separated by an insulator (dielectric). When voltage is applied, electrons are forced onto one plate and removed from the other, charging the capacitor and creating an electric field between the electrodes. The electric field's energy is stored in the capacitor's dielectric. The energy stored in a capacitor is used to reduce changes in voltage, just as an overflow pond will reduce changes in a river's level.

Capacitance measures the amount of energy that a capacitor stores for a given amount of charge and voltage. The area of the electrodes and the material used for the dielectric determine the capacitor's ability to store energy. More area or a thinner dielectric increases capacitance. Like resistors, a capacitor's value comes with a tolerance in percent that allows it to vary around the labeled or nominal value.

All capacitor types may be just two separated electrodes, but the way they are manufactured gives them a wide range of electrical characteristics. The length and configuration of the electrodes adds a small amount of unwanted or parasitic