Lec02-2

# Lec02-2 - cture 2-1 COULOMB FORCE 1 2 2 ˆ q q F k r r = r...

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Unformatted text preview: cture 2-1 COULOMB FORCE 1 2 2 ˆ q q F k r r = r Charge q 1 “Test Charge” q 2 r 1,2 1,2 1,2 Question : How can q 1 sense q 2 without direct contact? • NO! just as air around us, there’re some medium around a charge, the electric field that transfers the force. “Is action at a distance possible?” cture 2-2 READING QUIZ 1 HOW DOES THE MAGNITUDE OF THE ELECTRIC FIELD E FROM A POINT CHARGE Q DEPEND ON THE MAGNITUDE OF Q AND THE DISTANCE R TO THE FIELD POINT? A) E = k Q Q / R 2 A) E = k Q / R B) E = k Q / R 2 C) E = k Q Q / R A) E = k Q / R 3 cture 2-3 Electric Field Define electric field , which is independent of the test charge, q 2 , and depends only on position in space: F E q = ur ur 2 1 ˆ 4 F Q E r q r πε = = r r Electric Field due to a Point Charge Q cture 2-4 Electric Field Lines • A visualization tool to illustrate the geometry of an electric field. • Electric field lines originate from positive charges and terminates at negative charges . • The direction of the electric field at any location is tangential to the field line there. • The magnitude of the electric field at any location is proportional to the density of the lines there. # lines/area ~ 1/r 2 ~ |E| (or at infinity) cture 2-5 Electric Field With this concept, we can “map” the electric field anywhere in space A Vector field 77 82 83 68 55 66 83 75 80 90 91 75 71 80 72 84 73 57 88 92 77 56 88 73 64 cture 2-6 Demonstration Vandegraaff Generator and Insulators and Conductors cture 2-7 Electric field lines of two charges of equal magnitude dipole Far from the charges, electric...
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## This note was uploaded on 12/07/2011 for the course PHYS 241 taught by Professor Wei during the Fall '08 term at Purdue.

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Lec02-2 - cture 2-1 COULOMB FORCE 1 2 2 ˆ q q F k r r = r...

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