1. Magnetic Fields Gauss’s Law vs. Ampere’s Law Ampere’s Law Ampere’s Law for long straight wire Examples Magnetic properties of materials Force between 2 parallel wires Motors Loudspeakers

2. Magnetism and Induction Flowchart lawchangefieldCurrentforcedirectexamples Force Law 1B →qv →F = qv x BRHR 1charge deflection picture tube Force Law 2B →il →F = il x BRHR 12 wires, motor, loudspeaker Ampere’s Law B = μ o i/2πr← iRHR 2electromagnet solenoid Faraday Induction d/dt →Φ = B*A →ε = dΦ/dt i = ε/R Lentzgenerator transformer Current creates magnetic field

3. Gauss’s vs. Ampere’s Law Gauss’s Law for closed surface – Flux lines penetrating closed surface equals charge enclosed. Ampere’s Law for closed loop – Magnetic field integrated along closed loop equals current enclosed.

4. Ampere’s Law for long straight wire

5. Right hand rule II Right hand rule for current carrying wire

6. Example 20-7

7. Example 20-8

8. Example 20-9

9. Magnetism in materials Spinning charge particle creates magnetic field If all spinning particles align, you have a magnet

10. Force between parallel wires - 1

11. Force between parallel wires - 2 a)currents same direction b)currents opposite direction action-reaction pair

12. Magnetism and Induction Flowchart lawchangefieldCurrentforcedirectexamples Force Law 1B →qv →F = qv x BRHR 1charge deflection picture tube Force Law 2B →il →F = il x BRHR 12 wires, motor, loudspeaker Ampere’s Law B = μ o i/2πr← iRHR 2electromagnet solenoid Faraday Induction d/dt →Φ = B*A →ε = dΦ/dt i = ε/R Lentzgenerator transformer Wire 1 creates magnetic field Wire 2 feels force of that field

13. Example 20-10

14. Example 20-11

15. Problem 41

16. Problem 43

17. Problem 45

18. Rotating current loop φ

19. DC motor Current reverses every half turn DC motor

20. DC Motor animation DC motor animation http://educypedia.karadimov.info/library/MccComplet.swf

21. Loudspeaker