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Homework Help: Electric field and charge.

  1. Sep 4, 2011 #1
    1. The problem statement, all variables and given/known data

    The electric field at the point x = 10.0 cm and y = 0 points in the positive x direction with a magnitude of 10.0 N/C. At the point x = 20.0 cm and y = 0 the electric field points in the positive x direction with a magnitude of 20.0 N/C. Assume that this electric field is produced by a single, point charge.

    (a) Find the location of the point charge.

    (b) Find the sign and magnitude of its charge.

    3. The attempt at a solution

    10 =q/4piε(d+10)^2

    20 = q/4piε(d)^2
    E is more at x=20 , so q must be -ve, and situated beyond x=20

    dividing both eqn , we get
    20/10 = d^2 + 100+ 20d/ d^2
    solving the quadratic eqn , we get
    d= 10±10√2
    d= 24.14cm
    put d= 24.14 in any above formula,

    we get q= -0.13nC

    Both answers are incorrect. I've gone to two different tutors and neither could help. Please help
  2. jcsd
  3. Sep 4, 2011 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Measure distances in meters, not cm.
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