ch18_magnetic

ch18_magnetic - CHAPTER 18:c18cof01 Magnetic Properties...

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c18cof01 Iron single crystal photomicrographs magnetic domains change shape as a magnetic field ( H) is applied. domains favorably oriented with the field grow at the expense of the unfavorably oriented domains. Magnetic Properties CHAPTER 18:
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ISSUES TO ADDRESS. .. How do we measure magnetic properties? What are the atomic reasons for magnetism? How are magnetic material classified? Materials design for magnetic storage. CHAPTER 18: MAGNETIC PROPERTIES
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18.1 Introduction Magnetism: attractions and repulsions between materials Known for thousands of years Mechanisms still debated Technological useful: generators, transformers, motors, radio, TV, telephones, computers, sound and video Examples: Iron Some steels Lodestone mineral To different degrees, all substances are influenced by magnetic fields
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c18f01 c18f01 Magnetic field lines of force around a current loop and a bar magnet. 18.2 Basic Concepts Magnetic forces appear when moving charges Forces can be represented by imaginary lines grouped as fields
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c18f02 MAGNETIC DIPOLES The magnetic moment represented by a vector
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c18f03 c18f03 Magnetic Field Vectors magnetic field strength (H) & magnetic flux density (B) + = 0 0 M H B μ 0 r = H = M m χ magnetization magnetic susceptibility 1 - = r m relative permeability H = B 0 0 H = B Magnetic flux density l NI = H Magnetic field strength
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Electrical Devices Resistor R = V/I ohm = volt/ampere Capacitor C = ΔQ/ ΔV = I/(ΔV/ Δt) farad = coulomb/volt Inductor L = V/(ΔI/ Δt) henry = volt-second/Ampere = weber/ampere Related units weber = volt-second
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c18tf01 c18tf01
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B c18f04 Origins of Magnetic Moments: Responds to quantum mechanics laws Two main contributions: ( a) an orbiting electron and ( b) electron spin . The spin is an intrinsic property of the electron and it is not due to its rotation
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c18f05 Diamagnetic material in the presence of a field, dipoles are induced and aligned opposite to the field direction. Paramagnetic material
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ch18_magnetic - CHAPTER 18:c18cof01 Magnetic Properties...

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