- 107 Views
- Uploaded on
- Presentation posted in: General

Download Presentation
## PowerPoint Slideshow about '10 電磁 III ' - selima

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

### 10 電磁 III

### 敬請期待電磁 IV

How is an aurora so thin yet so tall and wide?

Sections

- 磁場
- 電流與磁場

10-1 磁場

- The electric field and the magnetic field
- Electromagnets and permanent magnets

Magnetic Field Lines

- Magnetic vs. electric dipoles

例 1 A 5.3 MeV proton

B = 1.2 mT

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

10-1.3 Crossed Fields: The Hall Effect

- By the conduction electrons in copper:

例 2 A cube generator

d = 1.5 cm, v = 4.0m/s, B = 0.05T

10-1.4A Circulating Charged Particle

例 3 The Mass Spectrometer (質譜儀)

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

CERN LHC

The LHC is 27km long and sits 100m below the surface.

10-1.6Magnetic Force on a Current-Carrying Wire

Magnetic Force

For a wire segment:

例 4 A length of wire with a semicircular arc

10-1.7Torque on A Current Loop

- F2 and F4 cancel
- F1 and F3 form a force couple

例 5 A galvanometer for analog meters

10-1.8The Magnetic Dipole

- The magnetic dipole moments
- The magnetic potential energy

10-2 Magnetic Fields due to Currents

Conventional rocket EM Rail Gun

dq

=

dE

pe

2

4

r

0

v

1

dq

v

=

d

E

r

pe

3

4

r

0

m

q

ids

sin

=

0

dB

p

2

4

r

v

v

m

id

s

r

=

0

dB

p

3

4

r

10-2.1 Calculating the Magnetic Field due to a currentThe law of Biot and Savart

Magnetic Field Due to a Current in a Long Straight Wire

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

例 6 What B does the current produce?

例 7 The Field Between Two wires

10-2.3 Ampere’s Law

- Comparing Gauss’ law and Ampere’s law
- Ampere’s law

The Magnetic Field Outside a Long Straight Wire with Current

The Magnetic Field Inside a Long Straight Wire with Current

例 7 A hollow conducting cylinder

10-2.4 Solenoids and Toroids

- Magnetic Field of a Solenoid (螺線管)
- Magnetic Field of a Toroid (螺線環)

磁圍阻核融合反應器

Tokamak Fusion Test Reactor

10-2.5 A Current Carrying Coil as a Magnetic Dipole

- A current loop and a bar magnet

Coulomb’s Law

- Using Gauss’s law to take advantage of special symmetry situations
- Gaussian surfaces
- 高斯面上各點電場與面內總電荷相關

Gauss’ Law

- Flux enclosed charge

Gauss’Law and Coulomb’Law

- From G.L. to C.L.