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Unformatted text preview: HW-3 1.Find the electric field a distance z above the center of circular disk of radius R which carries a uniform surface charge density . What does your formula give in the limit Rand zR. Solution:Obviously the electric field is in the z direction so we only need to calculate the z component of the electric field. For a ring between r and r+dr, its contribution to the z component electric field is 2/322222222)(2)(42cos)(4zrzrdrzrzzrrdrzrdqdEzThen the total electric field is 2/12222222/1222/3222/32211212112)(12)(2)(2zRzRzzRzzzrzzrrdrzzrzrdrdEERRRzFor R, 2Ewhich is expected because the disk is like an infinite sheet. For R, 222/122211zRzR, Thus222244zRzREwhich is expected because the disk is like a point charge of...
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This note was uploaded on 02/06/2010 for the course PHYSICS 11 taught by Professor Qiu during the Fall '09 term at University of California, Berkeley.
- Fall '09