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Unformatted text preview: Physics 106 – Final Review Modified from College Physics , 8 th Ed., Serway and Vuille. You should know all the concepts and equations in this summary. The Nature of Forces Force at a distance is explained by one of two types of models, Virtual Particle Models , and Geometric Models . Our best understanding of electromagnetic forces uses a virtual particle model called QED . Our best understanding of gravitational forces uses a geometrical model called General Relativity . Section 15.1: Properties of Electric Charges Electric charges have the following properties: 1. Unlike charges attract one another and like charges repel one another. 2. Electric charge is always conserved. 3. Charge comes in discrete packets that are integral multiples of the basic electric charge e . 4. The force between two charged particles is stronger when the charges are closer. When a charge is brought near an insulator, it can cause the charge to be polarized . Neutral objects can experience electrostatic force when charges are polarized. (This is why balloons stick to ceilings.) Section 15.2: Insulators and Conductors Conductors are materials in which charges move freely in response to an electric field. If charges remain fixed on atoms, the materials are called insulators . Section 15.3: Coulomb's Law Coulomb's law states that the electric force between two stationary charged point particles separated by a distance r has the magnitude 2 2 1 r q q k F e = [15.1] where  q 1  and  q 2  are the magnitudes of the charges on the particles in coulombs and k e is the Coulomb constant . The direction of the force is along the line of centers. It is attractive when the charges are opposite and repulsive when they are like. Coulomb’s law also works for charged spheres. Section 15.4: The Electric Field An electric field E is a set of vectors defined at every point in space. The electric field is defined by the equation: ⃗ = ⃗ [15.4] The direction of the electric field at a point in space is the direction of the electric force that would be exerted on a small positive charge placed at that point. The magnitude of the electric field due to a point charge q at a distance r from the point charge is 2 r q k E e = [15.6] Section 15.5: Electric Field Lines Electric field lines are useful for visualizing the electric field in any region of space. The electric field vector E is tangent to the electric field lines at every point. Furthermore, the electric field is stronger where electric field lines are closer together. Section 15.6: Conductors in Electrostatic Equilibrium A conductor in electrostatic equilibrium has the following properties: 1. The electric field is zero everywhere inside the conducting material....
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This document was uploaded on 12/15/2011.
 Fall '09
 Force

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