22 31. In the figure below, a non conducting rod of length & = 8.15 cm has a charge of -q = -4.23 fC uniformly distributed along its length. (a) What is the linear charge density of the rod? What are the (b) magnitude and (c) direction ( relative to the positive direction of the x axis) of the electric field produced at point , at a distance a = 120 em from the rod? What is the electric field magnitude produced at distance a = 50 m by (d) the rod and (e) a particle of charge -q= -4.23 f( that we use to replace the rod? (At that distance, the rod "looks" like a particle.) 22 37. Suppose you design an apparatus in which a uniformly charge disk of radius It is to produce an electric field. The field magnitude is most important along the central perpendicular axis of the disk, at a point / at a distance 2.00/2 from the disk (shown in figure (a) below). Crest analysis suggests that you switch to a ring of the same outer radius It but with inner radius //2.00 (figure (b)). Assume that the ring will have the same surface charge density as the original disk. if you switch to the ring, by what percentage will you decrease the electric field magnitude at PY Hint: Use superposition together with the fact that the magnitude of the electric field produced by a fat, circular, charged disk with radius h, surface charge density a, and measured a distance d away from the disk along its central aris, is given by: Enk(d) = 2 (1 Figure 12-17 Problem 37. 23 40. The figure below shows a very large nonconducting sheet that has a uniform surfaces: change density of = -2.00 pC/m ; it also shows a particle of charge Q = 6.00 p(, at distance d from the shoot. Both are fixed in place. If d = 0.200 m, at what: (a) positive and (b) negative coordinate on the I axis (other than infinity) is the net electric field Ers of the short and particle zero? (c) If d = 0.500 m, at what coordinate in the r axis is Fast = 0? A reminder that the equation for the electric field due to a plane of charge can be found on your formula sheet