Summarizing Capacitors and Dielectrics

Summary

• A capacitor is a device used to store charge.
• The amount of charge \(Q\) a capacitor can store depends on two major factors—the voltage applied and the capacitor’s physical characteristics, such as its size.
• The capacitance \(C\) is the amount of charge stored per volt, or

  \(C=\cfrac{Q}{V}.\)

• The capacitance of a parallel plate capacitor is \(C={\epsilon }_{0}\phantom{\rule{0.15em}{0ex}}\cfrac{A}{d}\), when the plates are separated by air or free space. \({\epsilon }_{\text{0}}\phantom{\rule{0.25em}{0ex}}\) is called the permittivity of free space.
• A parallel plate capacitor with a dielectric between its plates has a capacitance given by

  \(C={\mathrm{\kappa \epsilon }}_{0}\phantom{\rule{0.25em}{0ex}}\cfrac{A}{d},\)

  where \(\kappa \) is the dielectric constant of the material.
• The maximum electric field strength above which an insulating material begins to break down and conduct is called dielectric strength.

Glossary

capacitor

a device that stores electric charge

capacitance

amount of charge stored per unit volt

dielectric

an insulating material

dielectric strength

the maximum electric field above which an insulating material begins to break down and conduct

parallel plate capacitor

two identical conducting plates separated by a distance

polar molecule

a molecule with inherent separation of charge