A. Electric Nature of Matter
1. A positively charged rod is brought close to a neutral conducting sphere. What is the charge on A?
++++++++++++++++++ A
(A) positive (B) negative (C) neutral
Questions 2-3 A positively charged rod is brought close to two neutral conducting spheres connected by a wire.
++++++++++++++++++ A B
2. The wire is disconnected, and then the rod is removed. What are the charges on A and B?
(A) +A, -B (B) -A, +B (C) both neutral
3. The rod is removed first, and then the wire is disconnected. What are the charges on A and B?
(A) +A, -B (B) -A, +B (C) both neutral
4. Consider the two ways to charge a conductor.
a. Label the picture that illustrate conduction and the picture that illustrates induction
b. What could be done to make the metal rod in the right side set of pictures have a net negative charge?
5. A neutral glass rod is rubbed with a neutral piece of silk. The rod acquires an excess charge of + 1 mC. What is the excess charge on the piece of silk?
6. A positively charged piece of metal is used to charge a neutral piece of metal. Which technique, conduction or induction, can make the neutral metal…
positively charged?negatively charged?
B. Electric Force and Field
Question 7-12 Sphere B is r meters from sphere A, both of which have a charge of +1 C. The electric force between them is 1 N.
A r B
7. What is the direction of the force on B ?
(A) Ú (B) Ù
8. What is the magnitude of the force on B if QB increases to +2 C?
(A) ¼ N (B) ½ N (C) 2 N (D) 4 N
9. What is the magnitude of the force on A if QB is doubled?
(A) ¼ N (B) ½ N (C) 2 N (D) 4 N
10. What is the magnitude of the force on B if bothQA & QB are doubled?
(A) ¼ N (B) ½ N (C) 2 N (D) 4 N
QA = QB = +1 C
11. What is the magnitude of the force on B if r is doubled?
(A) ¼ N (B) ½ N (C) 2 N (D) 4 N
12. What is the magnitude of the force on B if r is halved?
(A) ¼ N (B) ½ N (C) 2 N (D) 4 N
Name:______
Per:______
Questions 13-17 An electron and proton are 1 m apart.
p 1 2 3 e
13. The proton's electric force compared to the electron is
(A) greater (B) equal (C) less
14. When the proton and electron are released, they move
(A) away from each other (B) toward each other
15. How does the electric force change as they move?
(A) increase (B) same (C) decrease
16. The acceleration of the electron compare to the proton is
(A) greater (B) equal (C) less
17. At which position will the proton and electron collide?
(A) 1 (B) 2 (C) 3
Questions 18-21 Sphere A, Q = +1 C and m = 0.4 kg, is suspended from the ceiling on a rope near a charged Wall. Forces F1 (weight), F2 (electric) and F3 (tension) act on A.
53o
F1
F2 A
F3
18. What the charge on the wall?
(A) positive (B) negative
19. What is F3?
(A) 3 N (B) 4 N (C) 5 N
20. What is F1?
(A) 3 N (B) 4 N (C) 5 N
21. What is F2?
(A) 3 N (B) 4 N (C) 5 N
Questions 22-24 The electric field strength is E at point p, which is r distance way from sphere A with charge +Q.
+Q • p
22. What is the direction of the electric field at p?
(A) Ú (B) Ù
23. If Q is doubled, what is the electric field at point p?
(A) ¼E (B) ½E (C) 2E (D) 4E
24. If r is doubled, what is the electric field at point p?
(A) ¼E (B) ½E (C) 2E (D) 4E
Questions 25-27 What is the direction of the electric field at point p half way between charges of equal magnitude?
25. +Q • p +Q
(A) Ù (B) Ú (C) E = 0
26. +Q • p –Q
(A) Ù (B) Ú (C) E = 0
27. –Q • p +Q
(A) Ù (B) Ú (C) E = 0
Questions 28-31 Consider the two unequal charges below. Where is the electric field equal to zero?
28. A +4Q B C –Q D
29. A –4Q B C –Q D
30. A +Q B C +4Q D
31. A +Q B C –4Q D
Questions 32-34 Consider the two offset charges below. What is the direction of electric field at point p?
32. +Q • p
+Q
(A) Ù (B) Ü (C) ß (D) Þ
33. +Q • p
–Q
(A) Ý (B) à (C) ß (D) Þ
34. –Q • p
–Q
(A) Ý (B) à (C) ß (D) Þ
Questions 35-37 Consider the four charges arranged in a box below. What is the direction of the field at point p, which is in the center of the box?
35. –Q +Q
• p
–Q +Q
(A) Ù (B) Ü (C) Ú (D) E = 0
36. +Q +Q
• p
+Q +Q
(A) Ù (B) Ü (C) Ú (D) E = 0
37. +Q –Q
• p
–Q +Q
(A) Ù (B) Ü (C) Ú (D) E = 0
38. In a simplified model of a hydrogen atom, an electron orbits a proton at a distance of 5.3 x 10-11 m.
a. What is the electric force between the electron and proton?
b. What is the gravitational force between the electron and proton? (G = 6.67 x 10-11 N•m2/kg2)
c. What is the velocity of the electron in its orbit?
39. Two small identical metal spheres contain excess charge of -10 mC and +8 mC, respectively (m = 10-6). The spheres are 0.4 m apart.
a. Determine the magnitude and direction of the force between the spheres.
The spheres touch and then returned to their original 0.4-m separation.
b. Determine the charge on each sphere.
c. Determine the magnitude and direction of the force between the spheres.
40. Two charged spheres of equal mass and charge, suspended from a common point by threads that are 0.5 m long, rest a distance of 0.5 m apart.
a. Label the three forces acting on the
right sphere (Fg, Ft, Fe) on the vector 30o
sum diagram below.
0.5 m
b. What is the charge on each sphere if the mass of each sphere is 0.030 kg?
41. What is the strength of an electric field inside a conductor?
42. Where is the net charge located on a good conductor?
43. What is the orientation of the electric field with respect to a conductor's surface?
44. The electric field lines are drawn around charged spheres and plates. Indicate whether the charged spheres or plates are positive or negative.
a. % # ( $ ' b.
! " " ! $ $ $ $ $ $ $ $
' $ ( # %
45. A 50 mC charge and a 1 mC charge are 0.1 m apart.
a. Which charge generates the stronger field at 0.1 m?
b. Which charge exerts the greater force on the other?
46. What is the electric field 3 m away from a +10mC charge?
47. Determine the magnitude and direction of the electric field at point p.
Q1 = -5 mC Q2 = +10 mC
•
1 m p 3 m
48. Determine the magnitude and direction of the electric field at point p.
Q1 = -5 mC
1 m Q2 = +10 mC
p •
3 m
49. Determine the magnitude and direction of the electric field at the center of a square 2 m on an edge if charges of +8 mC each are at three of the corners of the square.
+8mC 2 m +8 mC
2 m
+8mC
50. What is the magnitude and direction of the electric force on a -3 x 10-7 C charge in a 500 N/C electric field directed toward the west?
51. Calculate the magnitude and direction of the force on Q2.
Q1 = +10 mC Q2 = +2 mC Q3 = -10 mC
0 m 5 m 15 m
52. A +40 mC and -10 mC charge are 10 m apart.
+40 mC -10 mC
0 m 10 m
a. Determine the magnitude and direction of the electric field at a point half way between.
b. Determine where the electric field is zero.
53. A drop of water has a net charge of 150 electrons. What is its mass if it is suspended in an electric field is 300 N/C?
54. A particle of mass 1 x 10-6 kg has an excess charge of
+1 mC. The particle is located in a region between two oppositely charged parallel plates where the electric field is uniform and has a magnitude of 1000 N/C. Determine the
a. the force acting on the particle.
b. the acceleration of the particle.
The plates are 0.01 m apart and the particle is initially at rest at a point close to the positive plate.
c. Determine the velocity of the particle "just" before it strikes the negative plate.
55. What is the electric field 5 m away from a +10mC charge?
56. What is the electric force between an electron and proton that are 1.0 x 10-10 m apart?
57. What is the magnitude and direction of the electric force on a +5 x 10-7 C charge in a 200 N/C electric field directed toward the west?
58. A +32 mC and +8 mC charge are 2 m apart.
+32 mC +8mC
0 m 2 m
a. What is the electric force on the +8 mC charge?
b. What is the electric force on the +32 mC charge?
c. Which charge generates the stronger field at a point half way between the two charges?
d. Determine the magnitude and direction of the electric field at the midpoint.
A -1 mC charge is placed at the midpoint
e. Determine the magnitude and direction of the electric force on the -1 mC charge at the midpoint.
f. Determine where the -1 mC charge can be placed where it would experience a net electric force of zero.
59. A proton traveling at 3 x 106 m/s enters a region where the electric field has a magnitude of 3 x 105 N/C. The electric field is uniform and slows the proton's motion. Determine
a. the acceleration on the proton.
b. the distance the proton will travel before coming to a momentary halt.
c. the time required for the proton to travel this distance.
60. Q1 = +9 mC, and Q2 = +1 mC, are located on the x-axis at
x = 0 m and x = 6 m, respectively.
Q1 = +9 mC Q2 = +1mC
0 m 6 m
a. Determine where a third charge, Q3 = +1 mC, can be placed and experience no net force.
b. Charge Q2 is replaced with a -1 mC charge located at
x = 6 m. Determine where a third charge, Q3 = +1 mC, can be placed and experience no net force.
C. Electric Potential Energy and Voltage
61. A proton and electron are released within a constant electric field generated between parallel plates.
p
+ –
e
Which has more kinetic energy when it reaches the plate?
(A) electron (B) proton (C) tie
62. Which system has +Ue?
+ – + + – –
A B C
(A) A (B) B (C) C (D) B and C
63. Which pair of equal charges takes positive work to bring together from a very large initial distance apart?
+ – + +
A B
(A) A (B) B (C) A and B
Questions 64-66 Consider the square with four equal charges on the corners.
+ – + + + –
+ – + + – +
A B C
64. Which arrangement has V > 0 at the center?
(A) A (B) B (C) C (D) none
65. Which arrangement(s) is V = 0 at the center?
(A) A (B) B (C) C (D) A and C
66. Which arrangement(s) is V = 0 and E = 0 at the center?
(A) A (B) B (C) C (D) A and C
Questions 67-69 A charge particle is placed at point p in the electric field, whose direction is indicated by the dashed arrows. The particle is moved along equal length paths indicated by the solid arrows.
A
B C
p
67. Which path increases Ue for a positively charged particle?
(A) A (B) B (C) C (D) B and C
68. Which path decreases Ue for a negatively charged particle?
(A) A (B) B (C) C (D) B and C
69. Which path does not change Ue for any charged particle?
(A) A (B) B (C) C (D) B and C
70. Which point(s) have the same potential as point X around these two equal put opposite charges?