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Unformatted text preview: Chapter 24 – Capacitance and Dielectrics Capacitors and capacitance Capacitors in series and parallel Energy storage in capacitors and electric field energy Dielectrics Molecular model of induced charge Gauss law in dielectrics 1. Capacitors and Capacitance Capacitor: device that stores electric potential energy and electric charge.  Two conductors separated by an insulator form a capacitor.  The net charge on a capacitor is zero.  To charge a capacitor  , wires are connected to the opposite sides of a battery. The battery is disconnected once the charges Q and –Q are established on the conductors. This gives a fixed potential difference V ab = voltage of battery. Capacitance: constant equal to the ratio of the charge on each conductor to the potential difference between them. ab V Q C = Units: 1 Farad (F) = Q/V = C 2 /J = C 2 /N m Capacitance is a measurement of the ability of capacitor to store energy (V = U / q). Capacitors in Vacuum Parallel Plate Capacitor: uniform electric field between the plates, charge uniformly distributed over opposite surfaces A Q E o o ε ε σ = = d A V Q C ab ε = = A Qd d E V o ab ε 1 = ⋅ = ε = 8.85 x 1012 F/m The capacitance depends only on the geometry of the capacitor. The capacitance depends only on the geometry of the capacitor....
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 Spring '08
 SAHA
 Physics, Capacitance, Charge, Energy

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