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Unformatted text preview: Lecture 36 More Example of Electric Potential. Equipotentials. Lightning rods and why you lose your radio station inside tunnels. Example: Getting the electric field from the electric potential =  r r E V ( 29 = + + r 2 5 2( 4 ) E x z i j x z k We saw last time that =  + + 2 2 ( , , ) 2 5 4 V x y z x xz y z Example: Find the electric field for =  = 2 2 x V E x z x =  =  5 y V E y =  =  + 2 8 z V E x z z Equipotentials for a positive point charge 30 V 20 V 10 V E Equipotentials Topographic map of Mt. Fuji Equipotentials for a positive point charge 30 V 20 V 10 V x y V 2D mapping of potential: E E X A X B Take two points A and B on an equipotential surface The electric field is always perpendicular to equipotential surfaces For any path between A and B on the surface, A B B A V V E dl =  = v r v must be per pendicular t o E dl r r25001000500250 500 250 1000 2500 It is actually an electric fish! The figure below looks (more or less) like the equipotentials of: A. Two identical charges B. A dipole C. Two charges of equal sign but different magnitude 100100 ACT: Equipotentials25001000500250 500 250 1000 2500 The electric field points in the direction of decreasing potential and is perpendicular to the equipotential surfaces: + Black ghost knife fish This fish uses the electric field to detect approaching preys or...
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 Fall '08
 HerreraSiklody
 Electric Potential, Light

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