1. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Chapter 33. The Magnetic Field Digital information is stored on a hard disk as microscopic patches of magnetism. Just what is magnetism? How are magnetic fields created? What are their properties? These are the questions we will address. Chapter Goal: To learn how to calculate and use the magnetic field.

2. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Topics: Magnetism The Discovery of the Magnetic Field The Source of the Magnetic Field: Moving Charges The Magnetic Field of a Current Magnetic Dipoles Ampère’s Law and Solenoids The Magnetic Force on a Moving Charge Magnetic Forces on Current-Carrying Wires Forces and Torques on Current Loops Magnetic Properties of Matter Chapter 33. The Magnetic Field

3. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Chapter 33. Reading Quizzes

4. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. What is the SI unit for the strength of the magnetic field? A.Gauss B.Henry C.Tesla D.Becquerel E.Bohr magneton

5. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. What is the SI unit for the strength of the magnetic field? A.Gauss B.Henry C.Tesla D.Becquerel E.Bohr magneton

6. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. What is the shape of the trajectory that a charged particle follows in a uniform magnetic field? A.Helix B.Parabola C.Circle D.Ellipse E.Hyperbola

7. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. What is the shape of the trajectory that a charged particle follows in a uniform magnetic field? A.Helix B.Parabola C.Circle D.Ellipse E.Hyperbola

8. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The magnetic field of a point charge is given by A.Biot-Savart’s law. B.Faraday’s law. C.Gauss’s law. D.Ampère’s law. E.Einstein’s law.

9. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The magnetic field of a point charge is given by A.Biot-Savart’s law. B.Faraday’s law. C.Gauss’s law. D.Ampère’s law. E.Einstein’s law.

10. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The magnetic field of a straight, current-carrying wire is A.parallel to the wire. B.inside the wire. C.perpendicular to the wire. D.around the wire. E.zero.

11. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The magnetic field of a straight, current-carrying wire is A.parallel to the wire. B.inside the wire. C.perpendicular to the wire. D.around the wire. E.zero.

12. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Chapter 33. Basic Content and Examples

13. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

16. Tactics: Right-hand rule for fields

17. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The Source of the Magnetic Field: Moving Charges The magnetic field of a charged particle q moving with velocity v is given by the Biot-Savart law: where r is the distance from the charge and θ is the angle between v and r. The Biot-Savart law can be written in terms of the cross product as

18. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.1 The magnetic field of a proton QUESTION:

19. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.1 The magnetic field of a proton

20. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.1 The magnetic field of a proton

21. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.1 The magnetic field of a proton

22. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.1 The magnetic field of a proton

23. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.1 The magnetic field of a proton

24. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The Magnetic Field of a Current The magnetic field of a long, straight wire carrying current I, at a distance d from the wire is The magnetic field at the center of a coil of N turns and radius R, carrying a current I is

25. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Problem-Solving Strategy: The magnetic field of a current

26. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Problem-Solving Strategy: The magnetic field of a current

27. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Problem-Solving Strategy: The magnetic field of a current

28. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Problem-Solving Strategy: The magnetic field of a current

29. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.4 The magnetic field strength near a heater wire QUESTION:

30. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.4 The magnetic field strength near a heater wire

31. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.4 The magnetic field strength near a heater wire

32. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.4 The magnetic field strength near a heater wire

33. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

34. Tactics: Finding the magnetic field direction of a current loop

35. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Magnetic Dipoles The magnetic dipole moment of a current loop enclosing an area A is defined as The SI units of the magnetic dipole moment are A m 2. The on-axis field of a magnetic dipole is

36. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.7 The field of a magnetic dipole QUESTIONS:

37. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.7 The field of a magnetic dipole

38. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.7 The field of a magnetic dipole

39. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.7 The field of a magnetic dipole

40. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Tactics: Evaluating line integrals

41. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Ampère’s law Whenever total current I through passes through an area bounded by a closed curve, the line integral of the magnetic field around the curve is given by Ampère’s law:

42. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The strength of the uniform magnetic field inside a solenoid is where n = N/l is the number of turns per unit length.

43. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The Magnetic Force on a Moving Charge The magnetic force on a charge q as it moves through a magnetic field B with velocity v is where α is the angle between v and B.

44. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

45. Magnetic Forces on Current-Carrying Wires Consider a segment of wire of length l carrying current I in the direction of the vector l. The wire exists in a constant magnetic field B. The magnetic force on the wire is where α is the angle between the direction of the current and the magnetic field.

46. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.13 Magnetic Levitation QUESTION:

47. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.13 Magnetic Levitation

48. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.13 Magnetic Levitation

49. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. EXAMPLE 33.13 Magnetic Levitation

50. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

51. Chapter 33. Summary Slides

52. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. General Principles

53. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. General Principles

54. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. General Principles

55. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Applications

56. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Applications

57. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Applications

58. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Chapter 33. Clicker Questions

59. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Does the compass needle rotate clockwise (cw), counterclockwise (ccw) or not at all? A.Clockwise B.Counterclockwise C.Not at all

60. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. A.Clockwise B.Counterclockwise C.Not at all Does the compass needle rotate clockwise (cw), counterclockwise (ccw) or not at all?

61. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The magnetic field at the position P points A.Into the page. B.Up. C.Down. D.Out of the page.

62. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. A.Into the page. B.Up. C.Down. D.Out of the page. The magnetic field at the position P points

63. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The positive charge is moving straight out of the page. What is the direction of the magnetic field at the position of the dot? A.Left B.Right C.Down D.Up

64. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. A.Left B.Right C.Down D.Up The positive charge is moving straight out of the page. What is the direction of the magnetic field at the position of the dot?

65. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. What is the current direction in this loop? And which side of the loop is the north pole? A.Current counterclockwise, north pole on bottom B.Current clockwise; north pole on bottom C.Current counterclockwise, north pole on top D.Current clockwise; north pole on top

66. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. A.Current counterclockwise, north pole on bottom B.Current clockwise; north pole on bottom C.Current counterclockwise, north pole on top D.Current clockwise; north pole on top What is the current direction in this loop? And which side of the loop is the north pole?

67. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. A.Left B.Into the page C.Out of the page D.Up E.Down An electron moves perpendicular to a magnetic field. What is the direction of ?

68. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. A.Left B.Into the page C.Out of the page D.Up E.Down An electron moves perpendicular to a magnetic field. What is the direction of ?

69. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. What is the current direction in the loop? A.Out of the page at the top of the loop, into the page at the bottom. B.Out of the page at the bottom of the loop, into the page at the top.

70. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. A.Out of the page at the top of the loop, into the page at the bottom. B.Out of the page at the bottom of the loop, into the page at the top. What is the current direction in the loop?

71. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Which magnet or magnets produced this induced magnetic dipole? A. a or d B. a or c C. b or d D. b or c E. any of a, b, c or d

72. Copyright © 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. A. a or d B. a or c C. b or d D. b or c E. any of a, b, c or d Which magnet or magnets produced this induced magnetic dipole?