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Unformatted text preview: fierro (jmf2547) HW 06 berk (60290) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points A closed surface with dimensions a = b = . 554 m and c = 0 . 6648 m is located as in the figure. The electric field throughout the region is nonuniform and given by vector E = ( + x 2 ) where x is in meters, = 2 N / C, and = 4 N / (C m 2 ). E y x z a c b a What is the magnitude of the net charge enclosed by the surface? Correct answer: 1 . 28109 10 11 C. Explanation: Let : a = b = 0 . 554 m , c = 0 . 6648 m , = 2 N / C , and = 4 N / (C m 2 ) . The electric field throughout the region is directed along the x-axis and the direction of d vector A is perpendicular to its surface. Therefore, vector E is parallel to d vector A over the four faces of the surface which are perpendicular to the yz plane, and vector E is perpendicular to d vector A over the two faces which are parallel to the yz plane. That is, only the left and right sides of the right rectangular parallel piped which encloses the charge will contribute to the flux. The net electric flux through the cube is = integraldisplay right side E x d A - integraldisplay left side E x d A = a b bracketleftbig + ( a + c ) 2- - a 2 bracketrightbig = a b (2 a c + c 2 ) = a b c (2 a + c ) = (0 . 554 m) (0 . 554 m) (0 . 6648 m) [4 N / (C m 2 )] [2 (0 . 554 m) + 0 . 6648 m] = 1 . 44687 N m 2 / C , so the enclosed charge is q = = [8 . 85419 10 12 C 2 / (N m 2 )] (1 . 44687 N m 2 / C) = 1 . 28109 10 11 C . 002 10.0 points Which of the following is true about the net force on an uncharged conducting sphere in a uniform electric field? 1. It produces a torque on the sphere about the direction of the field....
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This note was uploaded on 09/19/2008 for the course PHY 303L taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
- Spring '08