Three point-like charges are placed at the corners of a square as shown in the figure, 28.0 cm on each side. Find the minimum amount of work required by an external force to move the charge q1 to infinity. Let q1=-2.10 μC, q2=+2.40 μС, q3=+3.60 μC.

A point charge of -4.00 nC is at the origin, and a second point charge of 6.00 nC is on the x axis at x= 0.820 mm . Find the magnitude and direction of the electric field at each of the following points on the x axis.  x2 = 19.0 cm

Four point-like charges are placed as shown in the figure, three of them are at the corners and one at the center of a square, 36.0 cm on each side. What is the electric potential at the empty corner? Let q1=q3=+26.0 µС, q2=-28.0 μC, and q4=-48.0μc V