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ñ 0 E) + ñ Ans: E Difficulty: Medium SectionDef: Section 18-1, 18-2, 18-3, 18-4 4. Each of three objects has a net charge. Objects A and B attract one another. Objects B and C also attract one another, but objects A and C repel one another. Which one of the following table entries is a possible combination of the signs of the net charges on these three objects? A B C A) + + ñ B) ñ + + C) + ñ ñ D) ñ + ñ E) ñ ñ + Ans: D Difficulty: Easy SectionDef: Section 18-1, 18-2, 18-3, 18-4 5. A conducting sphere has a net charge of ñ6.4 ◊ 10 ñ17 C. What is the approximate number of

positive negative C) negative positive D) negative negative E) zero zero Ans: C Difficulty: Medium SectionDef: Section 18-1, 18-2, 18-3, 18-4 11. Consider three identical metal spheres, A , B , and C . Sphere A carries a charge of -2.0 µ C; sphere B carries a charge of -6.0 µ C; and sphere C carries a charge of +4.0 µ C. Spheres A and B are touched together and then separated. Spheres B and C are then touched and separated. Does sphere C end up with an excess or a deficiency of electrons and how many electrons is it? A) deficiency, 6 ◊ 10 13 B) excess, 3 ◊ 10 13 C) excess, 2 ◊ 10 13 D) deficiency, 3 ◊ 10 12 E) There is no excess or deficiency of electrons. Ans: E Difficulty: Medium SectionDef: Section 18-1, 18-2, 18-3, 18-4 12. Two charged particles A and B are located near one another. Both the magnitude and direction of the force that particle A exerts on particle B is independent of A) the sign of charge B . B) the sign of charge A . C) the distance between A and B . D) the magnitude of the charge on B .

18. Three charges are positioned as indicated in the figure. What are the horizontal and vertical components of the net force exerted on the +15 µ C charge by the +11 µ C and +13 µ C charges? horizontal vertical A) 95 N 310 N B) 76 N 310 N C) 250 N 130 N D) 95 N 130 N E) 76 N 370 N Ans: E Difficulty: Hard SectionDef: Section 18-5 19. A ñ4.0- µ C charge is located 0.45 m to the left of a +6.0- µ C charge. What is the magnitude and direction of the electrostatic force on the positive charge? A) 2.2 N, to the right B) 2.2 N, to the left C) 1.1 N, to the right D) 1.1 N, to the left E) 4.4 N, to the right Ans: D Difficulty: Medium SectionDef: Section 18-5

B) b C) c D) d E) e Ans: E Difficulty: Medium SectionDef: Section 18-5 Reference: Ref 18-1 The figure shows an equilateral triangle ABC . A positive point charge + q is located at each of the three vertices A , B , and C . Each side of the triangle is of length a . A point charge Q (that may be positive or negative) is placed at the mid-point between B and C . 25. Is it possible to choose the value of Q ( that is non-zero ) such that the force on Q is zero? Explain why or why not. A) Yes, because the forces on Q are vectors and three vectors can add to zero. B) No, because the forces on Q are vectors and three vectors can never add to zero. C) Yes, because the electric force at the mid-point between B and C is zero whether a charge is placed there or not. D) No, because the forces on Q due to the charges at B and C point in the same direction. E) No, because a fourth charge would be needed to cancel the force on Q due to the charge at A . Ans: E Refer To: Ref 18-1 Difficulty: Easy SectionDef: Section 18-5 26. Determine an expression for the magnitude and sign of Q so that the net force on the charge at A is zero newtons. A) B) C)

32. Two particles of the same mass carry charges +3 Q and -2 Q , respectively. They are shot into a region that contains a uniform electric field as shown. The particles have the same initial velocities in the positive x direction. The lines, numbered 1 through 5, indicate possible paths for the particles. If the electric field points in the negative y direction, what will be the resulting paths for these particles? A) path 1 for +3 Q and path 4 for ñ2 Q B) path 3 for +3 Q and path 2 for ñ2 Q C) path 4 for +3 Q and path 3 for ñ2 Q D) path 2 for +3Q and path 5 for ñ2Q E) path 5 for +3Q and path 2 for ñ2Q Ans: E Difficulty: Hard SectionDef: Section 18-6, 18-7, 18-8 Reference: Ref 18-2 Five particles are shot from the left into a region that contains a uniform electric field. The numbered lines show the paths taken by the five particles. A negatively charged particle with a charge ñ3 Q follows path 2 while it moves through this field. Do not consider any effects due to gravity. 33. In which direction does the electric field point? A) toward the top of the page B) toward the left of the page C) toward the right of the page D) toward the bottom of the page E) out of the page, toward the reader Ans: D Refer To: Ref 18-2 Difficulty: Medium

Ans: E Refer To: Ref 18-3 Difficulty: Medium SectionDef: Section 18-6, 18-7, 18-8 39. If a +2.0 ◊ 10 ñ5 C point charge is placed at P , what is the force exerted on it? A) 0.2 N, toward the negative plate B) 0.2 N, toward the positive plate C) 5 ◊ 10 4 N, toward the positive plate D) 5 ◊ 10 4 N, toward the negative plate E) 5 ◊ 10 4 N, into the plane of the page Ans: A Refer To: Ref 18-3 Difficulty: Medium SectionDef: Section 18-6, 18-7, 18-8 40. A small sphere of mass 2.5 ◊ 10 ñ5 kg carries a total charge of 6.0 ◊ 10 ñ8 C. The sphere hangs from a silk thread between two large parallel conducting plates. The excess charge on each plate is equal in magnitude, but opposite in sign. If the thread makes an angle of 30 ∞ with the positive plate as shown, what is the magnitude of the charge density on each plate? A) 2.5 ◊ 10 ñ9 C/m 2 B) 5.2 ◊ 10 ñ9 C/m 2 C) 1.0 ◊ 10 ñ9 C/m 2 D) 2.1 ◊ 10 ñ8 C/m 2 E) 4.2 ◊ 10 ñ8 C/m 2 Ans: D Difficulty: Hard SectionDef: Section 18-6, 18-7, 18-8

counterclockwise non-zero Ans: B Difficulty: Hard SectionDef: Section 18-6, 18-7, 18-8 46. Which one of the following statements is true concerning the spacing of the electric field lines in the vicinity of two point charges of equal magnitude and opposite sign? A) The spacing indicates the direction of the electric field. B) The spacing does not depend on the magnitude of the charges. C) The spacing is large when the magnitude of the charges is large. D) The spacing indicates the relative magnitude of the electric field. E) The spacing is small when the magnitude of the charges is small. Ans: D Difficulty: Easy SectionDef: Section 18-6, 18-7, 18-8 47. Which one of the following statements is true concerning the electrostatic charge on a conductor? A) The charge is uniformly distributed throughout the volume. B) The charge is confined to the surface and is uniformly distributed. C) Most of the charge is on the outer surface, but it is not uniformly distributed. D) The charge is entirely on the surface and it is distributed according to the shape of the object. E) The charge is dispersed throughout the volume of the object and distributed according to the object's shape. Ans: D Difficulty: Easy SectionDef: Section 18-6, 18-7, 18-8 48. The magnitude of the electric field at a distance of two meters from a negative point charge is E . What is the magnitude of the electric field at the same location if the magnitude of the charge is doubled?

A) E /4 B) E /2 C) E D) 2 E E) 4 E Ans: D Difficulty: Easy SectionDef: Section 18-6, 18-7, 18-8 49. What is the magnitude and direction of the electric force on a ñ3.0 µ C charge at a point where the electric field is 2800 N/C and is directed along the + y axis. A) 0.018 N, ñ y direction B) 0.012 N, + y direction C) 0.0084 N, ñ y direction D) 0.0056 N, + y direction E) 0.022 N, + x direction Ans: C Difficulty: Medium SectionDef: Section 18-6, 18-7, 18-8 50. A conducting sphere carries a net charge of +6 µ C. The sphere is located at the center of a conducting spherical shell that carries a net charge of ñ2 µ C. Determine the excess charge on the outer surface of the spherical shell. A) ñ4 µ C B) +4 µ C C) ñ8 µ C D) +8 µ C E) +6 µ C Ans: B Difficulty: Medium SectionDef: Section 18-6, 18-7, 18-8

51. A cubical Gaussian surface is placed in a uniform electric field as shown in the figure. The length of each edge of the cube is 1.0 m. The uniform electric field has a magnitude of 5.0 ◊ 10 8 N/C and passes through the left and right sides of the cube perpendicular to the surface. What is the total electric flux that passes through the cubical Gaussian surface? A) 5.0 ◊ 10 8 N ◊ m 2 /C B) 3.0 ◊ 10 9 N ◊ m 2 /C C) 2.5 ◊ 10 6 N ◊ m 2 /C D) 1.5 ◊ 10 7 N ◊ m 2 /C E) zero N ◊ m 2 /C Ans: E Difficulty: Easy SectionDef: Section 18-9 52. What is the electric flux passing through a Gaussian surface that surrounds a +0.075 C point charge? A) 8.5 ◊ 10 9 N ◊ m 2 /C B) 6.8 ◊ 10 8 N ◊ m 2 /C C) 1.3 ◊ 10 7 N ◊ m 2 /C D) 4.9 ◊ 10 6 N ◊ m 2 /C E) 7.2 ◊ 10 5 N ◊ m 2 /C Ans: A Difficulty: Medium SectionDef: Section 18-9 53. A uniform electric field with a magnitude of 125 000 N/C passes through a rectangle with sides of 2.50 m and 5.00 m. The angle between the electric field vector and the vector normal to the rectangular plane is 65.0 ∞ . What is the electric flux through the rectangle? A) 1.56 ◊ 10 6 N ◊ m 2 /C

B) 6.60 ◊ 10 5 N ◊ m 2 /C C) 1.42 ◊ 10 5 N ◊ m 2 /C D) 5.49 ◊ 10 4 N ◊ m 2 /C E) 4.23 ◊ 10 4 N ◊ m 2 /C Ans: B Difficulty: Medium SectionDef: Section 18-9 54. A straight, copper wire has a length of 0.50 m and an excess charge of ñ1.0 ◊ 10 ñ5 C distributed uniformly along its length. Find the magnitude of the electric field at a point located 7.5 ◊ 10 ñ3 m from the midpoint of the wire. A) 1.9 ◊ 10 10 N/C B) 1.5 ◊ 10 6 N/C C) 6.1 ◊ 10 13 N/C D) 7.3 ◊ 10 8 N/C E) 4.8 ◊ 10 7 N/C Ans: E Difficulty: Hard SectionDef: Section 18-9 55. A total charge of ñ6.50 µ C is uniformly distributed within a sphere that has a radius of 0.150 m. What is the magnitude and direction of the electric field at 0.300 m from the surface of the sphere? A) 2.89 ◊ 10 5 N/C, radially inward B) 6.49 ◊ 10 5 N/C, radially outward C) 4.69 ◊ 10 5 N/C, radially inward D) 9.38 ◊ 10 5 N/C, radially outward E) 1.30 ◊ 10 6 N/C, radially inward

Ans: A Difficulty: Medium SectionDef: Section 18-9 56. A circular loop of wire with a diameter of 0.626 m is rotated in a uniform electric field to a position where the electric flux through the loop is a maximum. At this position, the electric flux is 7.50 ◊ 10 5 N ◊ m 2 /C. Determine the magnitude of the electric field. A) 8.88 ◊ 10 5 N/C B) 1.07 ◊ 10 6 N/C C) 2.44 ◊ 10 6 N/C D) 4.24 ◊ 10 6 N/C E) 6.00 ◊ 10 6 N/C Ans: C Difficulty: Medium SectionDef: Additional Problems 57. A helium nucleus is located between the plates of a parallel-plate capacitor as shown. The nucleus has a charge of +2e and a mass of 6.6 ◊ 10 ñ27 kg. What is the magnitude of the electric field such that the electric force exactly balances the weight of the helium nucleus so that it remains stationary? A) 4.0 ◊ 10 ñ7 N/C B) 6.6 ◊ 10 ñ26 N/C C) 2.0 ◊ 10 ñ7 N/C D) 5.0 ◊ 10 ñ3 N/C E) 1.4 ◊ 10 ñ8 N/C Ans: C Difficulty: Hard SectionDef: Additional Problems

58. Two identical conducting spheres carry charges of +5.0 μ C and ñ1.0 μ C, respectively. The centers of the spheres are initially separated by a distance L . The two spheres are brought together so that they are in contact. The spheres are then returned to their original separation L . What is the ratio of the magnitude of the electric force on either sphere after the spheres are touched to that before they were touched? A) 1/1 B) 4/5 C) 9/5 D) 5/1 E) 4/9 Ans: B Difficulty: Hard SectionDef: Additional Problems Reference: Ref 18-4 Two point charges, A and B , lie along a line separated by a distance L . The point x is the midpoint of their separation. 59. Which combination of charges would yield the greatest repulsive force between the charges? A) ñ2q and ñ4q B) +1q and ñ3q C) ñ1q and ñ4q D) ñ2q and +4q E) +1q and +7q Ans: A Refer To: Ref 18-4 Difficulty: Medium SectionDef: Additional Problems

60. Which combination of charges will yield zero electric field at the point x ? A) +1q and ñ1q B) +2q and ñ3q C) +1q and ñ4q D) ñ1q and +4q E) +4q and +4q Ans: E Refer To: Ref 18-4 Difficulty: Medium SectionDef: Additional Problems Reference: Ref 18-5 A solid, conducting sphere of radius a carries an excess charge of +6 µ C. This sphere is located at the center of a hollow, conducting sphere with an inner radius of b and an outer radius of c as shown. The hollow sphere also carries a total excess charge of +6 µ C. 61. Determine the excess charge on the inner surface of the outer sphere (a distance b from the center of the system). A) zero coulombs B) ñ6 μ C C) +6 μ C D) +12 μ C E) ñ12 μ C Ans: B Refer To: Ref 18-5 Difficulty: Medium SectionDef: Additional Problems 62. Determine the excess charge on the outer surface of the outer sphere (a distance c from the center of the system). A) zero coulombs

B) ñ6 μ C C) +6 μ C D) +12 μ C E) ñ12 μ C Ans: D Refer To: Ref 18-5 Difficulty: Hard SectionDef: Additional Problems 63. Which one of the following figures shows a qualitatively accurate sketch of the electric field lines in and around this system? A) a B) b C) c D) d E) e Ans: C Refer To: Ref 18-5 Difficulty: Medium SectionDef: Additional Problems