Three identical point charges, as shown, are placed at the vertices of an isosceles right angled triangle. Which of the numbered vectors coincides in direction with the electricfield at the mid-point M of the hypotenuse?

EA = Electric field at M due to charge placed at AEB = Electric field at M due to charge placed at BEC = Electric field at M due to charge placed at CAs seen from figure, EB→=EC→- So net electric field at M, Enet =EA , i.e., in the direction of vector 2.