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Unformatted text preview: 210 Chapt. 27 Currents and Resistance a) In which direction does each kind of ion move? b) Given that the conductivity of the air is given by σ = 2 . 70 × 10 − 14 Ω − 1 m − 1 , what is the current density? c) Assume that the ions have the same drift speed which is plausible since they are in the same electric field, have about the same mass on average, the same absolute value of charge, and about the same collision time on average. Recall in that vector J = nqvectorv d , where n is carrier density, q is carrier charge, and vectorv d is the drift velocity. What is this drift speed in our case? (Note that current is net flux of charge, not flux of one kind or another of charge. Be careful about signs.) 027 qfull 00300 1 3 0 tough math: deriving Ohm’s law 5. We will now derive Ohm’s law in its usual form (which is what one means when one just says Ohm’s law without qualification) from the microscopic form of Ohm’s law. The microscopic form of Ohm’s law is vector J = σ vector...
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This note was uploaded on 11/16/2011 for the course PHY 2053 taught by Professor Buchler during the Fall '06 term at University of Florida.
 Fall '06
 Buchler
 Physics, Conductivity, Current, Resistance

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