1. Electrostatic Energy and Capacitance

2. Chapter Overview: b Electrostatic Potential Energy: 25-1 b Defining Capacitance: 25-2 b Electrostatic Energy and the energy stored in the electric field: 25-3 b Working With Capacitors: 25-4 b Dielectrics: 25-5

3. Electrostatic Potential Energy b Governing relation is energy of a point charge in a field: b We can use this to “cobble together” electrostatic potential energies of both discrete and continuous charge distributions

4. Defining Capacitance b Capacitance is a term that quantifies the amount of charge stored at a given potential: b C depends only on the “geometry” and composition of a conductor.

5. Examples... b C for a sphere radius R b C for a parallel plate b C for a coaxial cable

6. Electrostatic Field Energy b Capacitors also store energy: b The Electric Field itself contains energy. We can define the Electric Field Energy Density as:

7. Working With Capacitors b Capacitors can be arranged in both parallel and series configurations: seriesseries parallelparallel

8. Dielectrics b Introducing a medium (dielectric) between the plates in a parallel plate capacitor can increase the capacitance: