1. Magnetic Induction Transforming energy with magnetism

2. Lorentz Force Reminder F = qv  B Source: Griffith, The Physics of Everyday Phenomena F is directed out of the screen.

3. CPS Question B I What is the direction of the Lorentz force on the charges moving in this wire? A. B. C. D. E. F.

4. – Moving Creates a Potential v B induced potential +

5. Motional emf Moving a conductor through a magnetic field causes separation of charges. Back-emf (motional emf) in conductor cancels potential from motion  = l vB when l, v, B all orthogonal

6. Rotating Loop Creates Circuit B V V

7. B V V

8. Group Work a.At which position(s) does the most magnetic flux pass through the loop? b.At which position(s) does the magnetic flux through the loop change the fastest? abcde

9. Group Work c.What is the current direction at these points? abcde

10. Faraday’s Law Greatest flux  when perpendicular Fastest change in flux  /  t when parallel abcde

11. Rotation Powers a Generator v v Motion V V induces a potential which generates a current that charges the battery B through the field

12. Lenz’s Law Explains Generator   B changing field opposing field needed I

13. Current in a Field Feels a Force F B I

14. Loop in a Field Has Torque B I I

15. Torque Turns a Motor I I current I force F B

16. Group Work If the magnetic field intensifies, in what direction will the induced current be? B Which direction is the flux change? What current would oppose it? What is the Lorentz force on each side?

17. How a Microphone Works microphone geophone Flux inside loop becomes more

18. How a Loudspeaker Works loudspeaker induced motion of magnet current current- generated field attracts or repels magnet

19. Back Potential As the motor turns, back-potential  B /  t opposes  Faster rotation  more back potential  I B