Do Now: Copy and sketch the electric field between the spheres below.

1. Do Now: Copy and sketch the electric field between the spheres below. • How is an electric field sketched? • What give rise to an electric field? + + + + + + + + + + + +

2. Pick up compass • Hold level • Which way does it point? • Why? • Needle is a magnet!

3. Forces:Fnet on object causes acceleration. • Forces – act at distance • Field • Fg– attractive btw masses. • Fe – attractive/repulsive between objects w net + or - charge. • Fmag magnetic- attractive/repulsive between objects w net e- spin. Mag Poles • g = Fg/m. F on test mass. • E = Fe/q. + F on test charge. • B ~ motion of charges. Compass needle.

4. Magnetism

5. What is Magnetism? Magnetism is the force of attraction or repulsion of a material due to the motion of its electrons. Like all forces Fmag can be a Fnetthat causes acceleration & is measured in N.

6. All magnets have 2 Poles, N and S. • Like Repel • Opposite attract. • Play

7. Magnetic Fieldsregions of space around a magnet where magnetic materials feel a force.

8. Magnets create a force field which will deflect a compass needle. • Field lines point in the direction of the deflection of the compass needle. • Through Magnet.

9. The poles strongest force. Field lines are close where field is strong.

10. Mag field lines come out of N pole, go into S pole. • Lines never touch or cross • Only curves • Field lines called lines of flux. • Flux density shows field strength. • B is symbol

11. Ex: Make a rough sketch of the horseshoe magnet below. Sketch the field lines near the ends of the magnet.

12. More than 1 magnet – out of N, into S.

13. Earth has a mag. field. The north seeking end of a compass points toward Earth’s N geographic pole.

14. Earth’s north pole acts like south pole of bar magnet.

15. What causes magnetism?

16. Atoms have magnetic fields due to excess e- spin. • Groups of atoms join so that their magnetic fields are all going in the same direction. • These areas of atoms are called “domains”

17. When an unmagnetized substance is placed in a magnetic field, the substance can become magnetized. This happens when the spinning electrons line up in the same direction.

18. An unmagnetized substance looks like this…

19. While a magnetized substance looks like this…

20. Magnetize Clip – Induced Magnetism

21. Poles of a magnet always come in pairs!

22. How to break a magnet: 1. Drop it 2. Heat it This causes the domains to become random again!

23. Non-magnets with magnetic properties can be polarized in the presence of a magnetic field.Temporary Magnets. Magnetic Polarization N S N S

24. Hwk Intro Sheet.

25. Relationship of Electricity & Magnetism

26. Similarities of Magnetic (B) to Electric Fields (E) • field lines also called lines of flux. • Both attract opposite. Repel like. • Drop off with d2. • Both Polarize objects. • Flux density shows intensity of field. • Both vector quantities.

27. Differences • For B field, direction compass needle points. • E field direction + test charge would move • Magnet feels no force in static E field. • Charges feel no force in static B field. • Isolated poles do not exist. Isolated charges do.

28. Demos. • Currents Cause Field (wrapped compass). • Solenoids form bar magnet– Mag N. Pole. • Mag Field puts force on charges. • Moving Magnets cause potential difference and current flow.

29. Bill Nye Magnets 19 min • https://www.youtube.com/watch?v=rl9r2Ap9vOo • Minute Physics How do magnets work 6.5 minutes. Quantum • http://www.youtube.com/watch?v=hFAOXdXZ5TM

30. Good Explanation Electromagnetism 57 Min. • https://www.youtube.com/watch?v=bht9AJ1eNYc • Old Navy film How magnetism produce Electricity 7 min. • http://www.youtube.com/watch?v=uoQelu7XRjk

32. Charge and magnetic fields. • Stationary charges do not cause magnetic fields, but do cause electric fields. • Charges in motion…. • When a current flows charges move, B field generated. • B is perpendicular to wire.

33. Electromagnet • Current creates magnet.

34. Magnetic fields induce pd voltage/current flow. • Drop magnet into wire loop – current flows in loop. • Spin wire coils through magnets – current flows in magnet.

35. Sketching FieldsUse arrows to show the direction of compass needle deflection.

36. Field into the page X like tail of arrow.Field out of page … like tip of arrow.

39. Mag Field Direction around Wire.

41. 2nd Hand Rule:Wire loop – thumb in current direction. Fingers in B direction.

42. Solenoid – Coils of wire (can be wrapped around core of iron).

43. 3rd hand rule: Fingers in direction of current. Thumb points to magnetic N. Pole. Solenoids act like bar magnets.

44. Charged particles moving in B fields feel a force!!Force direction determined by hand rule three.

45. Fourth

46. Direction of mag force on q perpendicular to v vector & to B field.For +q place right hand fingers into field, thumb points to v, palm points to mag force.For – q use left hand.

47. Electron in mag field B.

48. Force is proportional to amount of charge on particle.

49. Force on current carrying wire.The current in a wire also feels a force in mag field.

50. Fifth hand rule:–force direction on wire: fingers into field, thumb in current direction, palm points toward force direction.