CourseNotes.22 - 6.4.1 Energy Density During the semester,...

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Unformatted text preview: 6.4.1 Energy Density During the semester, we have encountered many different densities: mass density, volume charge density, and surface charge density to name a few. We will also end up encountering many more because it is always nice to talk about a quantity which extends over a finite region of space as a quantity which is defined at each point in space. Since the electric field between capacitor plates is extended over a finite region of space, it is natural to think about the energy stored in it in the same way. We will use a lowercase u to denote energy density. For a parallel plate capacitor u = U Ad = CV 2 2 Ad = 1 2 V d 2 = 1 2 E 2 (21) Although we have derived this formula for a parallel plate capacitor, it is actually always valid. Hence, anytime we establish an electric field we can think of it as storing energy and that energy is given by equation 21 6.5 Dielectric Materials Up until now in our discussion of electrostatics we have implicitly considered everything to be happening in a vacuum (or in air which is very close to a vacuum). Since we live in a world fullhappening in a vacuum (or in air which is very close to a vacuum)....
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This note was uploaded on 12/05/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.

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