Act.02.23 - density through this cross section varies with...

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Physics 2102, February 23, 2011. Activity 1: The figure shows four situations in which positive and negative charges move horizontally, and gives the rate at which each charge moves. (i) For each situation, indicate the direction of the net current. (ii) Rank the magnitude of the current in the four cases: I d > I b > I c > I a I a > I d > I c > I b I a = I b = I c > I d I a = I b = I c = I d Activity 2: The figure shows a portion of a circuit. Find the magnitude and direction of the current i in the lower, right-hand wire? Activity 3: Part (a) of the figure shows the cross section of a wire with radius R . The (magnitude of the) current
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Unformatted text preview: density through this cross section varies with radius r as J = ar 2 . We want to calculate the current through the outer part of the wire, between radius R/2 and R . To do this we must set up an integral over J • dA (i) What are the directions of the current density J and the area vector dA in this case? (ii) Part (b) shows a differential area dA of the wire, in the shape of a thin ring. Express dA in terms of radius r . (iii) Set up the integral over the current density and calculate the current through the outer part of the wire:...
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This note was uploaded on 05/20/2011 for the course PHYS 2102 taught by Professor Gimmnaco during the Fall '08 term at LSU.

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