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Unformatted text preview: a , carrying current I out of the page. Cable B has a solid cylindrical inner conductor, also of radius a and carrying total current I out of the page, but distributed uniformly over its cross section. a. Compare the BFeld magnitudes in the two cables at a distance r from the symmetry axis, where a < r < b . Are they the same? If not, which is larger? How do you know? b. Do the same for r < a . c. Which cable has the larger selfinductance? How do you know? a. By Ampere’s law, at distance r the Feld has magnitude μ I /2 π r in both cases. b. In cable A the Feld is zero for r < a , but not in case B. c. The stored energy in the BFeld is the same for both everywhere except for r < a , where it is zero for cable A but positive for cable B. Thus cable B has more stored energy for the same current, and thus has larger selfinductance. A B Physics 54 Summer 2011 2...
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 Summer '09
 Thomas
 Physics, Current, Inductance, Energy, Magnetic Field, Electric charge, Ampere, Magnetic Field Energy

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