Three equal negative point charges are placed at three of the corners of a square of side d as shown in the figure. Which of the arrows represents the direction of the net electric field at the center of the square?
A) A
B) B
C) C
D) D
E) The field is equal to zero at point P.

Question

Three equal negative point charges are placed at three of the corners of a square of side d as shown in the figure. Which of the arrows represents the direction of the net electric field at the center of the square? 
A) A 
B) B 
C) C 
D) D 
E) The field is equal to zero at point P.

Quizplus · Accepted Answer

Since all three charges are negative and symmetrical, the electric fields due to the two charges that are diagonal to the center of the square cancel out, leaving only the electric field due to the charge directly opposite to the center. This electric field points towards the center of the square, as shown in option C. Therefore, the net electric field at the center of the square points towards the center of the square, which is represented by option C.

Three Equal Negative Point Charges Are Placed at Three of the Corners