In the diagram, q1 = -3.33*10^-9 C and q2 = -5.22*10^-9 C. The electric field at point P is zero. What is the distance from P to q2? Q1~P~Q2 (left to right). Q1 to p has a distance of 0.255 m.

Answer 1

The electric field intensity at a point p is given by E = kQ1/d₁² + kQ2/d₂² where k is the coulomb constant, Q1 and Q2 the charges in coulombs, d the distance from each Q to the point P.

If E = 0, kQ1/d₁² = kQ2/d₂². As the k's cancel, and d₁ = 0.255 m, after substituting the values for Q1 and Q2 and solving for d₂² gives

d₂² = -5.22 x 10^-9C x 0.255²m² / -3.33 x 10^-9C = 0.1019 m²

Taking the square root of d₂² = 0.319 m