1. Chapter 24 Magnetic Fields

2. Magnet A substance that has polarity

3. Polarity Charge separation that results in one end being positive & the other end being negative

4. Magnets The ends are called the north & south poles

5. Magnets North pole = (+) South pole = (-)

6. Magnets Opposite poles attract & like poles repel

7. Some metals can become temporary magnets by bringing them close to a strong magnet

8. Most Permanent magnets are made of ALNICO, an alloy of Al, Ni, & Co

9. Very strong, but expensive permanent magnets are made of neodymium

10. Magnetic Field Space where attractive & repulsive forces act around a magnet

11. Magnetic Field Force fields similar to gravitational & electric fields

12. Magnetic Flux The number of field lines passing through a surface

13. Field Strength Magnetic field strength is proportional to the flux per unit area

14. A temporary magnet concentrates magnetic field lines and is attracted to a permanent magnet

15. A temporary magnet repels magnetic field lines and is repelled from a permanent magnet

16. Electromagnetism Electric current generates a magnetic field & vice versa

17. Hans Christian Oersted First to observe electromagnetic properties

18. Electromagnetism Electric field lines & magnetic field lines are perpendicular

19. First Right-Hand Rule Explain (page 497)

20. Passing a current through a wire wrapped around a piece of metal generates a magnetic field

21. Electromagnet Magnet generated by passing a current through a coiled wire

22. Second Right- Hand Rule Explain (page 498)

23. Magnetism at the atomic level Results from magnetic fields of electrons

24. Domain A group of about 10 20 atoms acting together electromagnetically

25. Domain Each domain acts like a dipole (polar unit)

26. Magnitism Magnetism occurs when domains are aligned

27. Passing a current through a wire in a magnetic field exerts a force

28. Third Right-Hand Rule Explain (page 503)

29. Magnetic Induction (B) Strength of a magnetic field

30. Magnetic Force Proportional to current, field strength, & length of the wire

31. Magnetic Force F = BIL

32. Magnetic Induction (B) B = F/IL

33. Magnetic Induction (B) Measured in teslas (T)

34. Tesla (T) T = N/Am

35. Galvanometer Device used to measure very small currents

36. Galvanometer Passing current through a looped wire in a magnetic field creates a force causing the wire to rotate (page 505)

37. Galvanometers Use 3RHR to force a needle to move as current passes through a MF

38. Galvanometers Can measure currents as small as 10 -6 A

39. Galvanometers Cannot rotate more than 180 o or more than 90 o from parallel to B

40. Electric Motors Must be able to spin 360 o Explain (page 506)

41. Electric Motor Force F = nBIL

42. F = force n = # of loops B = magnetic field strength I = current L = length of wire loop

43. Force on a single charged particle F = Bqv

44. F = force B = Field strength q = charge v = velocity