Download
1 / 73
730 likes | 927 Views
11 電磁 IV. How did the electric guitar revolutionize rock? From acoustic to electric guitars. Sections. 電磁感應 物質的磁性 麥斯威爾方程式 電磁波 Lasers and X-rays. 11-1.1 Two symmetric Situations. current loop + magnetic field → torque torque + magnetic field → current.
E N D
11 電磁 IV How did the electric guitar revolutionize rock? From acoustic to electric guitars
Sections • 電磁感應 • 物質的磁性 • 麥斯威爾方程式 • 電磁波 • Lasers and X-rays
11-1.1Two symmetric Situations • current loop + magnetic field → torque • torque + magnetic field → current
11-1.2 Two Experiments First ExperimentA Magnet is moving with respect to the loop.
Second Experiment The switch S is closed or opend.
11-1.3Faraday’s Law of Induction • An emf is induced when the number of magnetic field lines that pass through the loop is changing. – A Quantitative Treatment – The magnetic flux
例1 A solenoid contains a coil • i =1.5 A n = 2.2×104 turns/m • A = 3.46 ×10-4m2 N = 130 turns • 電流在25ms內穩定降至0
計算 • i =1.5 A n = 2.2×104 turns/m • A = 3.46 ×10-4m2 N = 130 turns • 電流在25ms內穩定降至0
11-1.4Lenz’s Law 感應電流所生的磁場與感應出該電流的磁場反向 • Opposition to pole Movement • Opposition to flux change • Electric Guitars
例2 B = 4.0 t2 +2.0 t + 3.0 Ebat = 2.0V r = 0.20m
例3B = 4 t2 x2 W = 3.0m H = 2.0m t = 0.1s
11-1.5Induction and Energy Transfers The work done by the applied force and the thermal energy produced in the wire.
11-2.1 Magnetism of Matter How can a clay-walled kiln reveal Earth’s magnetic field of the past?
11-2.2 The Magnetic field of the Earth The earth’s dipole field The mid-atlantic ridge
11-2.3 Magnetic Materials • Diamagnetism (逆磁性) • Paramagnetism (順磁性) • Ferromagnetism (鐵磁性)
11-2.4 Diamagnetism 逆磁性材料產生之磁矩與外磁場逆向，如外磁場非均勻，其將受到由強磁場區到弱磁場區之斥力。
11-2.5 Paramagnetism • 順磁性材料產生之磁矩與外磁場順向，如外磁場非均勻，其將受到由弱磁場區到強磁場區之吸力。 • 液態氧被吸在兩個磁極之間
11-2.6 Ferromagnetism • 鎳的磁域(magnetic domain)
11-3.2線積分與面積分 (安培迴路和高斯面) 磁場環流量 (安培定律) 電場通量 電場環流量 磁場通量 法拉第定律
11-3.3Magnets and magnetic flux (磁鐵和磁通量) Magnetic dipole: north/south pole
11-3.4Gauss’ Law for Magnetic Fields The net magnetic flux thru any closed Gaussian surface is zero.
11-3.5Gauss’ Law for electric Fields Flux enclosed charge
11-3.6Induced Magnetic Fields 3 ways to produce a magnetic field: by an electric current, by a magnetic material, and by induction.
11-4.1 Electromagnetic Waves • The Oscillating E and B Fields • A Most Curious Wave –The ether (以太)
11-4.2 Characteristics • Light Electromagnetic Waves • Hertz (赫茲)– Radio Waves • The Electromagnetic Spectrum • The Relative Sensitivity of Human eyes 430nm – 690nm
11-4.4 Comets What shapes the curved dust tail of a comet?
11-4.5Polarization (偏振) • Polarized Light • The Plane of Polarization • Linear, Circular and Elliptical polarization
