1. 27 Magnetic Sources charge motion Gauss’s Law (again) Ampere’s Law
materials

2. 27-1 The Magnetic Field of Moving Point Charges

3. Current & Magnetic Field
field circulation

4. (RHR) I  B

5. field-effect ammeter

6. RHR Review
Magnetic Force: cross-product rule (flat hand or “peanut butter jar”)
Magnetic Field: thumb along I, B follows curled fingers

7. moving point charge
B ~ qvsinq/r2.

8. 27-2 The Magnetic Field of Currents: The Biot-Savart Law

9. Biot-Savart Law integrated field effect of current
all dB same direction at center of hoop

10. B on axis of hoop dB not same direction
non-axial component adds vectorially to 0
axial component remains

11. section-view of hoop-current
axial B same direction
is current in or out of screen at top of hoop?

12. electromagnet (solenoid)

13. solenoid high# turns/meter N = #turns, L = length (m) Bcenter = moNI/L
n = N/L: Bcenter = monI

14. straight current-segment

15. Calculate B at Center in terms of L and I.

17. B of long straight current
angles are + and – 90 degrees:

18. parallel wires
same directed I’s attract, opposite directed currents repel.

19. Magnetic Force Balance Experiment

20. Magnetic Force Balance Experiment

21. the ampere
current in two long parallel wires that causes a force of 2x10-7 newtons per meter of length of the wires.

23. 27-3 Gauss’s Law for Magnetism

24. Gauss’s Law for B: Absence of Magnetic Charge
Compare to Gauss’s Law for E: Qinside

25. E and B Fields: Similarities and Differences

26. 27-4 Ampere’s Law

33. 27-5 Magnetism in Matter

34. Magnetic Moments of an Un-magnetized Material

35. Magnetic Domains in Crystalline Silicone

36. Aligned Magnetic Domains Produces “Magnet”

37. Magnetic Field due to Naturally Occurring Magnetite

38. Magnetic “bits” Recorded on Magnetic Tape… 0, 1, 0
Cross Section of a Recording Head Solenoid

39. Magnetic Disk Hard Drive

40. Magnetic Disk Hard Drive: 2400x Magnification

41. Summary magnetic fields are due to charge motion
biot-savart law determines B.
B fields have no point source
B integrated along a closed path is proportional to the current enclosed by the path
magnetic materials

42. general biot-savart

43. two hoops