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Explore the impact of electric guitars on rock music, from the transition from acoustic to electric, to electromagnetic principles, and the revolutionary sound transformation. Delve into Faraday’s Law of Induction, Lenz’s Law, and how electric guitars symbolize opposition and change in magnetic fields. Uncover the energy transfers and magnetic materials, revealing the essence of rock revolutionized by magnetic phenomena. Discover the harmonious blend of music and physics in the electrifying journey of rock evolution.
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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
