P219lecture04capacitors

# P219lecture04capacitors - Goal To understand the basics of...

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Unformatted text preview: Goal: To understand the basics of capacitors Objectives: 1) To learn about what capacitors are 2) To learn about the Electric fields inside a capacitor 3) To learn about Capacitance 4) To understand how a Dielectric can make a better Capacitor 5) To be able to calculate the Energy stored inside a capacitor What are capacitors? • Much like we build reservoirs to hold water you can build a device which holds onto charge. • These are capacitors. • They work by separating + and – charges so that you have an electric field between them. • Most commonly this is done on a pair of plates which are parallel to each other. Electric field inside a capacitor • The electric field is usually a constant between the plates of the capacitor. • This makes the math fairly straight forward. • The voltage across the capacitor is therefore V = E d where d is the separation between the plates. • Now we just need to find E. Electric Field • Each plate will have some amount of charge spread out over some area. • This creates a density of charge which is denoted by the symbol σ • σ = Q / A where Q is the total charge and A is the area • And E = 4π k σ • Also, E = σ / ε where ε is a constant (called the permittivity of free space ) Capacitance • Capacitance is a measure of how much charge you can store based on an electrical potential difference....
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## This note was uploaded on 12/01/2010 for the course PHYSICS 21900 taught by Professor Rhoads during the Spring '10 term at IUPUI.

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P219lecture04capacitors - Goal To understand the basics of...

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