Lecture_15

# Lecture_15 - Direction of Electric Field in a Wire E must...

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Does current fill the wire? Is E uniform across the wire? E must be parallel to the wire E is the same along the wire 0 3 2 3 1 = = Δ l d E l d E l d E l d E V A D D C C B B A ABCDA 0 0 V AB V CD 2 1 E E = Direction of Electric Field in a Wire

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E Bulb filament and wires are metals – there cannot be excess charges in the interior Are excess charges on the battery? nAuE i = E E What charges make the electric field in the wires? Electric Field in a Wire
Van de Graaff generator A Mechanical Battery Electron Current

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E E bends Field due to the Battery In the steady state there must be some other charges somewhere that contribute to the net electric field in such a way that the electric field points upstream everywhere.
Surface charge arranges itself in such a way as to produce a pattern of electric field that follows the direction of the wire and has such a magnitude that current is the same along the wire. nAuE i = Field due to the Battery

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Smooth transition from + surface charge to – to provide constant E . E Field due to Battery The amount of surface charge is proportional to the voltage.
The average magnitude of E in a closed circuit can vary from ~.01 V/m in copper wire to more than 100 V/m in Nichrome wire - due to a much different electron mobility. Surface charge at the end of a battery

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## This note was uploaded on 11/13/2009 for the course PHYS 17200 taught by Professor Gaboracsathy during the Spring '09 term at Purdue.

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Lecture_15 - Direction of Electric Field in a Wire E must...

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