Problem 3:   Four charges are arranged at the corners of a square.  Part (a)  Using the symmetry of the arrangement, determine the direction of the electric field at the center of the square due to the four charges at the corners, given that qa = qb = -2.1 μC and qc = qd = 2.1 μC .  Part (b)  Calculate the magnitude of the electric field, in newtons per coulomb, at the center of the square (the location of q), given that the square is 5.5 cm on a side.

A solid, insulating sphere of radius a has a uniform charge density throughout its volume and a total charge Q. Concentric with this sphere is an uncharged, conducting, hollow sphere whose inner and outer radii are b and c as shown in Figure P19.75. We wish to understand completely the charges and electric fields at all locations. (a) Find the charge contained within a sphere of radius r a. (b) From this value, find the magnitude of the electric field for r a. (c) What charge is contained within a sphere of radius r when a r b? (d) From this value, find the magnitude of the electric field for r when a r b. (e) Now consider r when b r c. What is the magnitude of the electric field for this range of values of r? (f) From this value, what must be the charge on the inner surface of the hollow sphere? (g) From part (f), what must be the charge on the outer surface of the hollow sphere? (h) Consider the three spherical surfaces of radii a, b, and c. Which of these surfaces has the largest magnitude of surface charge density?

Two solid spheres, both of radius 5 cm. carry identical total charges of 2 C. Sphere A is a good conductor. Sphere B is an insulator, and its charge is distributed uniformly throughout its volume, (i) How do the magnitudes of the electric fields they separately create at a radial distance of 6 cm compare? (a) EA EB= 0 (b) EA EB 0 (c) EA = EB 0 (d) 0EAEB (e) 0 = Ea EB (ii) How do the magnitudes of the electric fields they separately create at radius 4 cm compare? choose from the same possibilities as in part (i).

Three identical charges (q = 5.0 C.) lie along a circle of radius 2.0 m at angles of 30, 150, and 270, as shown in Figure P15.33 (page 524). What is the resultant electric field at the center of the circle? Figure P15.33

Charges of 3.00 nC, 2.00 nC, 7.00 nC, and 1.00 nC are contained inside a rectangular box with length 1.00 m, width 2.00 m, and height 2.50 m. Outside the box are charges of 1.00 nC and 4.00 nC. What is the electric flux through the surface of the box? (a) 0 (b) 5.64 102 N m2/C (c) 1.47 103 N m2/C (d) 1.47 103 N m2/C (e) 5.64 102 N m2/C

Two long, thin rods each have linear charge density = 6.0 C/m and lie parallel to each other, separated by 20.0 cm as shown in Figure P25.32. Determine the magnitude and direction of the net electric field at point P, a distance of 15.0 cm directly above the right rod. Figure P25.32

Three identical charges (q = 5.0 C.) lie along a circle of radius 2.0 m at angles of 30, 150, and 270, as shown in Figure P15.33 (page 524). What is the resultant electric field at the center of the circle? Figure P15.33

Consider the charge distribution shown in Figure P19.74. (a) Show that the magnitude of the electric field at the center of any face of the cube has a value of 2.18 keq/s2. (b) What is the direction of the electric field at the center of the top face of the cube?

A particle with charge q on the negative x axis and a second particle with charge 2q on the positive x axis are each a distance d from the origin. Where should a third particle with charge 3q be placed so that the magnitude of the electric field at the origin is zero?