Question

8. Find the location X on the x-axis (other than infinity) where the electric field goes to zero. a) Use little test arrows representing the two electric fields to determine if X lies to the left of q1, to the right of q2, or in between. Is the location of X likely to be closer to qi or q2? Place an X at a location on the x-axis satisfying the two concepts above. b) Sketch a distance, x, to represent the distance from qito X and (2 -x) to represent the distance from q2 to X. (See Fig. 15.7 if you have doubts) Write the magnitudes of Ei and E2 using the point charge electric c) field E - k but with qi, q2, and x involved. (2-x) d) Set these two electric field magnitudes equal to each other and cancel the k's. 91 (2-x) Cross-multiply by the denominators. qi ( -), ะเ2( )2 e) -- Take the square-root of both sides. f Take the square-root of both sides. q, g) Divide both sides by 4, h) Plug in the numbers for and solve for x. x 12 4i 9. a) A 20 cm X 30 cm sheet of paper in a copier machine has a uniform surface charge density of 5X103 C/m2. Find the approximate electric field 1 mm from the paper's surface. (Assume paper infinite compared to 1 mm) b) Repeat for a sheet of copper. c) What is the electric field inside the copper?

Answer 1