Question

  In the figure, charge q 1 = 2.1 × 10-6 C is placed at the origin and charge q 2 = -3.8 × 10-6 C is placed on the x-axis, at x = -0.20 m. Where along the positive x-axis can a third charge Q = -8.3 µC be placed such that the resultant force on this third charge is zero?

Answer 1

Let the third charge is placed at a distance x from first charge, then its distance from the second charge is (0.2+x) The force on third charge due to other two charges should be equal. Fi- F q1(x+0.2)q2 Taking square root 12 1x 10-6 (x + 0.2)--/3.8x10"(x) (0.0014 0.2) (0.0019 x0.0019-0.0014) 0.00028 0.00028 0.0005 -0.56m