Answer:
Explanation:
net force exerted on charge Q₃, exerted by charges Q₁and Q₂, will be zero
if net electric field due to charges Q₁ and Q₂ at origin is zero .
electric field due to Q₂
= 9 X 10⁹ X 3 x10⁹ / .04²
electric field due to Q₁
= 9 X 10⁹ X Q₁ / .02²
For equilibrium
9 X 10⁹ X Q₁ / .02² = 9 X 10⁹ X 3 x10⁻⁹ / .04²
Q₁ = 3 X10⁻⁹ x .02² / .04²
= 3 / 4 x 10⁻⁹
.75 x 10⁻⁹ C