A point charge Q = -500 nC and two unknown point charges,q₁ and q₂,are placed as shown in the figure.The electric field at the origin O,due to charges Q,q₁ and q₂,is equal to zero.The charge q₁ is closest to A) 130 nC. B) 76 nC. C) 150 nC. D) -76 nC. E) -130 nC.

Question

Quizplus · Accepted Answer

Since the electric field at point O is zero, the net charge at points S1 and U1 must be equal and opposite to the charge Q. Let's assume that the charge q₂ is closer to point S1 than U1. Then, the electric field due to Q and q₁ at point S1 would be attractive, and the electric field due to Q and q₂ at point S1 would be repulsive. Since the net electric field at point S1 is zero, the electric field due to q₁ and Q must be greater in magnitude than the electric field due to Q and q₂. Therefore, q₁ must be the larger magnitude charge, and since it is positive, the only choice that fits is A) 130 nC.

A Point Charge Q = -500 NC and Two Unknown