CHAPTER 18

Electrostatics

1 . A cubic Gaussian surface of side length x sits centered in a uniform electric field (E) between two
capacitor plates. The net electric flux through the Gaussian surface is
(A) 0
(B) Ex^2
(C) 2Ex^2
(D) 4Ex^2
(E) 6Ex^2

2 . Two spheres with charges +Q and –Q of equal magnitude are placed a vertical distance of d apart on
the y -axis, as shown in the figure. A third charge of +q is brought from a distance of x , where x >>d ,
horizontally toward the midpoint between +Q and –Q. The net force on +q as it is moved to the left
along the x -axis
(A) increases and continues in the same direction.
(B) increases and changes direction.
(C) remains the same magnitude and continues in the same direction.