Additional Problems

| 55 | An electric field of 260 000 N/C points due west at a certain spot. What are the magnitude and direction of the force that acts on a charge of at this spot?

| 56 | The force of repulsion that two like charges exert on each other is 3.5 N. What will the force be if the distance between the charges is increased to five times its original value?

| 57 | Conceptual Example 14 deals with the hollow spherical conductor in Figure 18-31. The conductor is initially electrically neutral, and then a charge + q is placed at the center of the hollow space. Suppose the conductor initially has a net charge of + 2q instead of being neutral. What is the total charge on the interior and on the exterior surface when the + q charge is placed at the center?

| 58 | At a distance r1 from a point charge, the magnitude of the electric field created by the charge is 248 N/C. At a distance r2 from the charge, the field has a magnitude of 132 N/C. Find the ratio r2/r1.

| 59 | ssm Background pertinent to this problem is available in Interactive LearningWare 18.3 at . A point charge is placed in an external uniform electric field of . At what distance from the charge is the net electric field zero?

| 60 | In a vacuum, two particles have charges of q1 and q2, where . They are separated by a distance of 0.26 m, and particle 1 experiences an attractive force of 3.4 N. What is q2 (magnitude and sign)?

| 61 | ssm Interactive LearningWare 18.1 at offers some perspective on this problem. Two tiny spheres have the same mass and carry charges of the same magnitude. The mass of each sphere is . The gravitational force that each sphere exerts on the other is balanced by the electric force. (a) What algebraic signs can the charges have? (b) Determine the charge magnitude.

| 62 | A charge of is located in an electric field. The x and y components of the electric field are and , respectively. (a) What is the magnitude of the force on the charge? (b) Determine the angle that the force makes with the + x axis.

* | 63 | Two charges are located along the x axis: at x1 = + 4.0 cm, and at x2 = − 4.0 cm. Two other charges are located on the y axis: at y3 = + 5.0 cm, and at y4 = + 7.0 cm. Find the net electric field (magnitude and direction) at the origin.

* | 64 | Four point charges have equal magnitudes. Three are positive, and one is negative, as the drawing shows. They are fixed in place on the same straight line, and adjacent charges are equally separated by a distance d. Consider the net electrostatic force acting on each charge. Calculate the ratio of the largest to the smallest net force.

* | 65 | A proton is moving parallel to a uniform electric field. The electric field accelerates the proton and thereby increases its linear momentum to from in a time of . What is the magnitude of the electric field?

* | 66 | Multiple-Concept Example 9 illustrates the concepts employed in this problem. A small object, which has a charge and mass , is placed in a constant electric field. Starting from rest, the object accelerates to a speed of in a time of 0.96 s. Determine the magnitude of the electric field.

* | 67 | ssm In the rectangle in the drawing, a charge is to be placed at the empty corner to make the net force on the charge at corner A point along the vertical direction. What charge (magnitude and algebraic sign) must be placed at the empty corner?

** | 68 | Two objects are identical and small enough that their sizes can be ignored relative to the distance between them, which is 0.200 m. In a vacuum, each object carries a different charge, and they attract each other with a force of 1.20 N. The objects are brought into contact, so the net charge is shared equally, and then they are returned to their initial positions. Now it is found that the objects repel one another with a force whose magnitude is equal to that of the initial attractive force. What is the initial charge on each object? Note that there are two answers.

Copyright © 2007 John Wiley & Sons, Inc. All rights reserved.