Lecture04

# Lecture04 - 1 Physics 132-Winter 2008 Prof Jim Beatty-Ohio...

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Unformatted text preview: 1 January 11, 2008 Physics 132-Winter 2008 Prof. Jim Beatty-Ohio State 1 Physics 132 Introductory Physics: Electricity and Magnetism Winter Quarter 2008 Lecture 4 January 11, 2008 Physics 132-Winter 2008 Prof. Jim Beatty-Ohio State 2 The Electric Field Coulomb’s Law allows us to calculate force on q due to other charges. F Qonq = kqQ r qQ 2 r E = r F q r F = q r E r E = kQ r 2 r F = kqQ j r j 2 j ∑ ) r j = q kQ j r j 2 j ∑ ) r j r E Faraday: Define a “field” proportional to the force felt by a “test charge” Units: Force/charge (N/C) 2 January 11, 2008 Physics 132-Winter 2008 Prof. Jim Beatty-Ohio State 3 Electric Field Lines Field lines are a way to visualize an E field. They begin on a + charge and end on a - charge. The E field is tangent to the field line. Field lines closer together ⇒ E is stronger A negative point charge January 11, 2008 Physics 132-Winter 2008 Prof. Jim Beatty-Ohio State 4 The Dipole +- Two equal and opposite charges with a slight separation between them form an electric dipole . 3 January 11, 2008 Physics 132-Winter 2008 Prof. Jim Beatty-Ohio State 5 Field Lines of an Electric Dipole Electric dipole: two point charges +q and -q separated by distance d No net charge (neutral), but creates E field anyway Many diatomic molecules act like dipoles (e.g. CO,NO,HCl) Axial symmetry +- +- Two adjacent equal dipoles: “quadrupole”; … January 11, 2008 Physics 132-Winter 2008 Prof. Jim Beatty-Ohio State 6 Electric Field on the Axis of a Dipole +q-q d E + E- P What is E field at point P? Add fields due to two charges: superposition z r E = r E + + r E − E + > E − at P r E + = + q 4 πε z − d 2 2 ) z r E − = − q 4 πε z + d 2 2 ) z r E = q 4 πε 1 z − d 2 2 − 1 z + d 2 2...
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## This note was uploaded on 04/18/2008 for the course PHYS 132 taught by Professor Beatty during the Winter '08 term at Ohio State.

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Lecture04 - 1 Physics 132-Winter 2008 Prof Jim Beatty-Ohio...

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