Lecture04-fall2011

# Lecture04-fall2011 - Fall 2010 Prof. Yong Chen (...

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Unformatted text preview: Fall 2010 Prof. Yong Chen ( [email protected] ) Prof. Michael Manfra ( [email protected] ) Lecture 2 Slide 1 PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http://www.physics.purdue.edu/academic_programs/courses/phys272/ PHYSICS 272 Electric & Magnetic Interactions Lecture 4 Charged Objects; Polarization of Atoms; Induced Dipoles [EMI 15.1-15.4] Fall 2010 Prof. Yong Chen ( [email protected] ) Prof. Michael Manfra ( [email protected] ) Lecture 2 Slide 2 PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http://www.physics.purdue.edu/academic_programs/courses/phys272/ Dipole Moment , , 2 4 1 3 1 r qs E πε = , , 4 1 3 2 r qs E πε- = x: y, z: Dipole moment: p = qs qs p = , , 2 4 1 3 1 r p E πε = , , 4 1 3 2 r p E πε- = , direction from –q to +q r>>s Dipole moment is a vector pointing from negative to positive charge The electric field of a dipole is proportional to the Fall 2010 Prof. Yong Chen ( [email protected] ) Prof. Michael Manfra ( [email protected] ) Lecture 2 Slide 3 PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http://www.physics.purdue.edu/academic_programs/courses/phys272/ Dipole in a Uniform Field E q F = Forces on +q and –q have the same magnitude but opposite direction =- + = E q E q F net It would experience a torque about its center of mass. What is the equilibrium position? Electric dipole can be used to measure the direction of electric field. Fall 2010 Prof. Yong Chen ( [email protected] ) Prof. Michael Manfra ( [email protected] ) Lecture 2 Slide 4 PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http://www.physics.purdue.edu/academic_programs/courses/phys272/ Choice of System Multiparticle systems: Split into objects to include into system and objects to be considered as external. To use field concept instead of Coulomb’s law we split the Universe into two parts: • the charges that are the sources of the field • the charge that is affected by that field Example: Oscilloscope Charges on metal plates are the sources of an uniform E field Fall 2010 Prof. Yong Chen ( [email protected] ) Prof. Michael Manfra ( [email protected] ) Lecture 2 Slide 5 PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http://www.physics.purdue.edu/academic_programs/courses/phys272/ What is the direction of the electric field at location X , due to the dipole? Question 1 A C B E D- + X iClicker Frequency Code: “AB” (before each lecture) Fall 2010 Prof. Yong Chen ( [email protected] ) Prof. Michael Manfra ( [email protected] ) Lecture 2 Slide 6 PHYS 272: Matter and Interactions II -- Electric And Magnetic Interactions http://www.physics.purdue.edu/academic_programs/courses/phys272/ Question 2 Locations 1 and 2 are equidistant from the center of the dipole. At which location is the magnitude of the electric field larger ?...
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## This note was uploaded on 09/13/2011 for the course PHY 172 taught by Professor Anderson during the Spring '10 term at Purdue University.

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Lecture04-fall2011 - Fall 2010 Prof. Yong Chen (...

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