Two small charged spheres A and B have charges 10 C and 40 C respectively and are held at separation of 90 ~cm from each other. At what distance from A , electric field intensity would be zero?

Step-by-step solution

The given situation is shown below, Let electric field at point P at a distance x from A is zero. At point P, E_ A =E_ B 1 4 ₀ q_ A x² = 1 4 ₀ q_ B (r-x)² 10 10⁻⁶ x² = 40 10⁻⁶ (r-x)² ( 1 x )²= ( 2 r-x )² 1 x = 2 r-x 2 x-r-x x= r 3 = 90 3 =30 ~cm