1. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnets and the magnetic field Electric currents create magnetic fields Magnetic fields of wires, loops, and solenoids Magnetic forces on charges and currents Magnets and magnetic materials Chapter 24 Magnetic Fields and Forces Topics: Sample question: This image of a patient’s knee was made with magnetic fields, not x rays. How can we use magnetic fields to visualize the inside of the body? Slide 24-1

2. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Force on a Charged Particle Moving in a Magnetic Field Slide 24-32

3. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Right-Hand Rule for Forces Slide 24-33

4. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Slide 24-34

5. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Paths of Charged Particles in Magnetic Fields Slide 24-35

6. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Mass Spectrometer Slide 24-36

7. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Fields Exert Forces on Currents Magnitude of the force on a current segment of length L perpendicular to a magnetic field Slide 24-37

8. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Forces between Currents Slide 24-38 Magnetic force between two parallel current-carrying wires

9. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Slide 24-39

10. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Forces between Current Loops Slide 24-40

11. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. A Current Loop Acts like a Bar Magnet Slide 24-41

12. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Fields Exert Torques on Current Loops Slide 24-42

13. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. 20.10 Applications: Galvanometers, Motors, Loudspeakers An electric motor also takes advantage of the torque on a current loop, to change electrical energy to mechanical energy.

14. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. The Torque on a Dipole in a Magnetic Field Slide 24-43

15. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Resonance Imaging Slide 24-44

16. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Magnetic Resonance Imaging Slide 24-45

17. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Electron Magnetic Moments: Ferromagnetism A nonmagnetic solid (copper)A ferromagnetic solid (iron) Slide 24-47

18. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Inducing a Magnetic Moment in a Piece of Iron Slide 24-48

19. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Summary of Chapter 20 Magnets have north and south poles Like poles repel, unlike attract Unit of magnetic field: tesla Electric currents produce magnetic fields A magnetic field exerts a force on an electric current:

20. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Summary of Chapter 20 A magnetic field exerts a force on a moving charge: Magnitude of the field of a long, straight current-carrying wire: Parallel currents attract; antiparallel currents repel

21. Copyright © 2007, Pearson Education, Inc., Publishing as Pearson Addison-Wesley. Summary of Chapter 20 Magnetic field inside a solenoid: Ampère’s law: Torque on a current loop: