# Lecture 04 - E Force due to E created by positive charge shifts electron cloud and nucleus in opposite directions electric dipole An atom is said

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Unformatted text preview: + E Force due to E created by positive charge shifts electron cloud and nucleus in opposite directions: electric dipole . An atom is said to be polarized when its electron cloud has been shifted by the influence of an external charge so that the electron cloud is not centered on the nucleus . Polarization of Atoms • it is not a permanent dipole • an induced dipole is created when a neutral object is polarized by an applied electric field An applied electric field creates induced dipoles: ! p = qs = ! ! E α- “ polarizability” of a material r r q E ˆ 4 1 2 1 1 !" = ! r r q p ˆ 4 1 2 1 ! "# = ! r r q E ˆ 2 4 1 5 1 2 2 ! "# \$ \$ % & ’ ’ ( ) = ! r r q F ˆ 2 4 1 5 2 1 2 1 ! "# \$ \$ % & ’ ’ ( ) = ! 1) 2) 3) 4) r r q F ˆ 2 4 1 5 2 1 2 2 ! "# \$ \$ % & ’ ’ ( ) * = ! 5) Neutral atoms are attracted by charges! Interaction strength ~ 1/r 5 r r q E ˆ 4 1 2 1 1 !" = ! r r q p ˆ 4 1 2 1 ! "# = ! r r q E ˆ 2 4 1 5 1 2 2 ! "# \$ \$ % & ’ ’ ( ) = ! r r q F ˆ 2 4 1 5 2 1 2 1 ! "# \$ \$ % & ’ ’ ( ) = ! 1) 2) 3) 4) r r q F ˆ 2 4 1 5 2 1 2 2 ! "# \$ \$ % & ’ ’ ( ) * = ! 5) Neutral atoms are attracted by charges! Interaction strength ~ 1/r 5 A Neutral Atom and a Point Charge Repulsion: r r q q F R ˆ 4 1 2 2 1 !" = ! F R Attraction: r r q N F A ˆ 2 4 1 5 2 1 2 ! "# \$ \$ % & ’ ’ ( ) * = ! F A Total: r r q N r q q F ˆ 2 4 1 4 1 5 2 1 2 2 2 1 !...
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## This note was uploaded on 02/10/2010 for the course PHYS 272h taught by Professor Staff during the Spring '08 term at Purdue University-West Lafayette.

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Lecture 04 - E Force due to E created by positive charge shifts electron cloud and nucleus in opposite directions electric dipole An atom is said

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