1. How is an aurora so thin yet so tall and wide?
10 電磁 III
How is an aurora so thin yet so tall and wide?

2. Sections 磁場
電流與磁場

3. 10-1 磁場 The electric field and the magnetic field
Electromagnets and permanent magnets

4. The definition of B

5. The tracks in a bubble chamber
Positron emitted-isotopes (C,N,O)
P annihilates with e, emits 2 gamma
Glucose usage in brain, schizophrenics（精神分裂症）

6. The SI unit for B 1 tesla = 1T =1 N/A‧m=104 gauss 108 T 1.5 T 10-2 T

7. Magnetic Field Lines Magnetic vs. electric dipoles
A horseshoe and a C-shaped magnets

8. 例 1 A 5.3 MeV proton
B = 1.2 mT
938 MeV
The rest mass energy of an electron is MeV

9. 10-1.2 Crossed Fields: Discovery of the Electron
A cathode ray tube
Thomson’s procedure:
設定E = 0, B = 0, 並記錄光點位置
開啟電場
開啟磁場,並調至與電場相等
1897 by JJ Thomson at Cambridge

10. Calculation

11. 10-1.3 Crossed Fields: The Hall Effect
By the conduction electrons in copper:
1879 by Hall (24) John Hopkins

12. 例 2 A cube generator d = 1.5 cm, v = 4.0m/s, B = 0.05T
Electrons shifted to the left, making the left side at lower potential

13. 10-1.4 A Circulating Charged Particle
B out of the page

14. 頻率與軌跡
The frequency and angular frequency
The magnetic bottle machine

15. Helical Paths
V∥ and V⊥
The pitch (螺距) of the helical path

16. 極光橢圓圈
Pink by N, green by O

17. 例 3 The Mass Spectrometer (質譜儀)

18. 質譜儀 Isotope Separation Centrifuge and diffusion chamber
x = m, V = V, B = mT
Isotope Separation
Centrifuge and diffusion chamber

19. 10-1.5 Cyclotrons and Synchrotrons
(迴旋加速器與同步加速器)
Fermilab: 6.3km ring

20. Synchrotrons The resonance condition: When proton energy > 50Mev:
Out of resonance (relativistic effect)
A huge magnet (4×106 m2) is needed for high energy (500Gev) protons
The proton sychrotron at Fermilab can produces 1Tev proton

21. 10-1.6 Magnetic Force on a Current-Carrying Wire

22. Magnetic Force
For a wire segment:

23. 例 4 A length of wire with a semicircular arc

24. Calculation

25. 線圈

26. 10-1.7 Torque on A Current Loop
F2 and F4 cancel
F1 and F3 form a force couple

27. 例 5 A galvanometer for analog meters

28. 10-1.8 The Magnetic Dipole The magnetic dipole moments
The magnetic potential energy

29. 磁能

30. 10-2 Magnetic Fields due to Currents
Conventional rocket EM Rail Gun

31. 10-2.1 Calculating the Magnetic Field due to a current
The law of Biot and Savart

32. Magnetic Field Due to a Current in a Long Straight Wire

33. Integration

34. Magnetic Field Due to a Current in a Circular Arc of Wire

35. 例 6 What B does the current produce?

36. 10-2.2 Two Parallel Currents

37. 例 7 The Field Between Two wires

38. Ampere’s Law
Comparing Gauss’ law and Ampere’s law
Ampere’s law

39. The Magnetic Field Outside a Long Straight Wire with Current

40. The Magnetic Field Inside a Long Straight Wire with Current

41. 例 7 A hollow conducting cylinder

42. 10-2.4 Solenoids and Toroids
Magnetic Field of a Solenoid (螺線管)
Magnetic Field of a Toroid (螺線環)

43. Magnetic Field of a Solenoid

44. Magnetic Field of a Toroid

45. 磁圍阻核融合反應器
Tokamak Fusion Test Reactor

46. 10-2.5 A Current Carrying Coil as a Magnetic Dipole
A current loop and a bar magnet

47. Magnetic Field of a Coil

48. 敬請期待 電磁 IV