PHY 2049 Midterm: University of Florida PHY 2049 exam4_sol_s07
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1 and 2, not 3 c. 1 and 3, not 2 d. 2 and 3, not 1 e. only 2. Solution: 1 and 2 are true, as shown by gauss" law. 23-20 (derived from gauss" law) e=(q/4 0)r/r3 since r=1/4 r, eat r is just. Of eat r=(q/4 0)(1/r2: a long straight wire is 2r long and carries current i upwards in the sketch. Solution: the field at point p is just double the field produced by either half of the wire, so choose the upper half, solve for b from this segment, and double the result. B = 2 0 db = 0i/2 0 sin ds/r2 where ds is some segment of the wire along its length between 0 and r (see fig. 29-5, p 767 in the text), is the angle between the straight wire and the vector r connected ds and point p. the magnitude r" is (s2 + r2)1/2 and sin =
