Equipment

1. Equipment • Compasses • Bar Magnets • Yellow Wire & power supply

2. Mr. Klapholz Shaker Heights High School Forces and Fields (6) In the most fundamental equations about the universe, we find fields. Black holes, the Aurora Borealis, and microwave ovens all are understood in terms of fields. Fields are abstract, but quite real.

3. MAGNETIC FORCE & FIELD (B)

4. Magnet basics • The poles of a magnet are the places where the field (B) is the greatest. • All magnets have two poles. If you try to break a magnet, you end up with two small magnets (each with a North and a South pole)

5. Compass • Perform a preliminary exploration. • Keep the compass off of your desktop; free your needle (it should shiver). • What does your compass do? • Slowly turn the compass’s container; what effect does this have on the needle? Do the letters or the numbers affect the needle? • The compass is measuring the Earth’s _ _ _ _ _ _ _ _ _ _ _ _ _ .

6. Compass • Perform a preliminary exploration. • Keep the compass off of your desktop. • What does your compass do? • Slowly turn the compass’s container; what effect does this have on the needle? Do the letters or the numbers affect the needle? • The compass is measuring the Earth’s Magnetic Field.

7. Compass • Perform a preliminary exploration. • Keep the compass off of your desktop. • What does your compass do? • Slowly turn the compass’s container; what effect does this have on the needle? Do the letters or the numbers affect the needle? • The compass is measuring the Earth’s Magnetic Field. • A compass is a _ _ _ _ _ _ _ _ _ _ _ _ _ detector.

8. Compass • Perform a preliminary exploration. • Keep the compass off of your desktop. • What does your compass do? • Slowly turn the compass’s container; what effect does this have on the needle? Do the letters or the numbers affect the needle? • The compass is measuring the Earth’s Magnetic Field. • A compass is a Magnetic Field detector.

9. How could we use a compassto get home?What exactly would we do? Home N W E S Start Here

10. Bar Magnet • Perform a preliminary exploration at your desk. • Does the bar have a magnetic field? How do you know?

11. ActivityThe most important pattern in magnetism:Map the Field due to a Bar Magnet N S

12. What does the field look like? [A, B, C] A

13. B

14. C

15. Yellow Wire • Does a wire make a magnetic field? • Does a current make a magnetic field? • Make the compass point toward the wire (!). • Is the field perpendicular or parallel to the wire? • Compare the field on one side of the current to the field on the other side. • Inside a current loop, is the field especially weak (due to subtraction / cancellation) or especially strong (due to addition / enhancement)? • All magnetism comes from _ _ _ _ _ _ _.

16. Yellow Wire • Does a wire make a magnetic field? • Does a current make a magnetic field? • Make the compass point toward the wire (!). • Is the field perpendicular or parallel to the wire? • Compare the field on one side of the current to the field on the other side. • Inside a current loop, is the field especially weak (due to subtraction / cancellation) or especially strong (due to addition / enhancement)? • All magnetism comes from CURRENT.

17. We have 3 big results: • The magnetic field never points toward the current. • The magnetic field is perpendicular to current. • The magnetic field on one side of a wire is opposite in direction to the field on the other side. How do we make sense of this? And… What does the field look like?

18. See how it agrees with our data. The Magnetic Field (B) due to a current (I) Pennsylvania State Univ. Wikipedia

19. Here is a current. What does the magnetic field look like? I

20. If you placed a compass next to one of the circles, is would align tangent to the circle. I B B Do you see that this accounts for the three big results? B B B

21. Now tilt that wire so it points at your eye. What would the magnetic field look like?

22. Here is the current. What would the magnetic field look like? I

23. I

24. Which way does the field go? I

25. I

26. Arrow Basics

27. Arrow Basics

28. Arrow Basics

29. What would you see if the arrow was aimed right at your eye?

31. What would you see if the arrow was away from your eye?

33. The Right-Hand Rule • Visualize the field loops around the current. • Put your right thumb in the direction of the current. • Your fingers will naturally curl in the direction of the magnetic field. Now go back and see how this agrees with the example that we did.

34. The current is moving away from you. I

35. The current is moving away from you. Fill in the 8 compasses. A B D I C

36. The current is moving away from you. Fill in the 8 compasses. A B D I C

37. Now tilt this wire so the current is going toward the left. What is the field above and below the wire? [Compare with the compasses A and C] A C Notice that in the plane of the paper, the field is well-defined

38. Now tilt this wire so the current is going toward the left. What is the field above and below the wire? [Compare with the compasses A and C] A C Notice that in the plane of the paper, the field is well-defined

39. Same Wire. In what direction is the field between you and the wire? Which compass is this [A, B, C, D]?

40. Same Wire. In what direction is the field between you and the wire? Which compass is this [A, B, C, D]?

41. Same Wire. In what direction is the field BEYOND the wire? Is this compass A, B, C, or D?

42. Same Wire. In what direction is the field BEYOND the wire? Is this compass A, B, C, or D?

43. Draw the field

48. Draw the field