Two charged particles of equal magnitude (+Q and −Q) are fixed at opposite corners of a square that lies in a plane (see figure below). A test charge +q is placed at a third corner.

Question

Two charged particles of equal magnitude (+Q and −Q) are fixed at opposite corners of a square that lies in a plane (see figure below). A test charge +q is placed at a third corner.
+Q
+q	−Q What is the direction of the force on the
test charge due to the two other charges?

drwls · Answer

45 degrees below the line connecting +q to -Q