# Lect06 - Physics 212 Lecture 6 Today's Concept Electric...

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Physics 212 Lecture 6, Slide 1 Physics 212 Lecture 6 Today's Concept: Electric Potential Defined in terms of Path Integral of Electric Field

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Physics 212 Lecture 6 Music Who is the Artist? A) John Prine B) Little Feat C) Taj Mahal D) Ry Cooder E) Los Lobos Why? Last time did Buena Vista Social Club (Cuba) Ry Cooder was the guy who brought them to our attention in this country Also, this album is great…. NOTE: Ellnora starts tonight…. .
Physics 212 Lecture 6, Slide 3 Your Comments 05 “I'm pretty sure my head just exploded. Just. .. everywhere.” “help! i need somebody help! not just anybody help! you know i need someone HELLPP" “That last one was a doozy. Equipotential lines seem like they hold the key to something, but I don't know what yet.” “Do we have to be able to use/do problems with gradients?” “Are we going to differentiate the electric potential in three dimensions in order to get the electric field?” “The calculations with the spherical insulator were hard to follow. And I understand simple ideas, but I hope that the lecture helps me understand more fully. Electric potential is related to energy – a key aspect of E’nM. We will use electric potential extensively when we talk about circuits. We really only need to know about derivatives (partial derivatives in a few cases). See example at end of class. Not too bad. After discussion today, I understand Gauss's Law!

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Physics 212 Lecture 6, Slide 4 BIG IDEA • Last time we defined the electric potential energy of charge q in an electric field: 40 - = - = Δ b a b a b a l d E q l d F U a a a a •The only mention of the particle was through its charge q . • We can obtain a new quantity, the electric potential, which is a PROPERTY OF THE SPACE , as the potential energy per unit charge. - = Δ Δ b a b a b a l d E q U V a a •Note the similarity to the definition of another quantity which is also a PROPERTY OF THE SPACE , the electric field. q F E a h
Physics 212 Lecture 6, Slide 5 Electric Potential from E field • Consider the three points A, B, and C located in a region of constant electric field as shown. 40 • What is the sign of Δ V AC = V C - V A ? (A) Δ V AC < 0 (B) Δ V AC = 0 (C) Δ V AC > 0 • Remember the definition: - = Δ C A C A l d E V a a • Choose a path (any will do!) D Δ x - - = Δ C D D A C A l d E l d E V a a a a 0 0 < Δ - = - = Δ x E l d E V C D C A a a

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When you integrate 0, you get 0, everywhere. Physics 212
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## This note was uploaded on 03/12/2012 for the course PHYS 212 taught by Professor Kim during the Fall '08 term at University of Illinois, Urbana Champaign.

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Lect06 - Physics 212 Lecture 6 Today's Concept Electric...

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