L33Magnet145s10

L33Magnet145s10 - Lecture 33: Magnetic Properties Reading...

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Lecture 33, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Reading assignment : C&R §18.1-18.8, §18.9-18.11 Learning objectives: Become familiar with basic magnetic phenomena: Magnetic field Magnetization Magnetic moment Domains Curie temperature Hysteresis loop Recognize characteristics of the following types of magnetism Diamagnetism Paramagnetism Antiferromagnetism Ferromagnetism Ferrimagnetism Know what distinguishes soft and hard magnetic materials, and the different types of applications for each Lecture 33: Magnetic Properties 1
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Lecture 33, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Basic Phenomena: Magnetic Field [C&R §18.2] Moving electric charges exert force on other moving electric charges Distinct from electrostatic force Magnetic field, H From current in a loop of wire From earth’s flowing, molten core From the spins and orbits of electrons in magnetically ordered substances Units on H : Amperes m –1 A m C&R Figure 18.1 2
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Lecture 33, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Inside a medium, magnetic fields generate magnetic induction, B Represents the magnitude of the field strength in a medium exposed to a magnetic field A.k.a. magnetic flux density Units on B : Teslas, T Relationship between B and H : μ : permeability of medium Basic Phenomena: Magnetic Induction [C&R §18.2] B = μ H In vacuum: µ 0 : permeability of vacuum, 4 π × 10 –7 Henry m –1 B 0 = μ 0 H 1 T = 1 N A m 1 H m = 1 N A 2 H m C&R Figure 18.3 3
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Lecture 33, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University To what extent does a material add to (or detract from) B 0 ? magnetization, M relative permeability, μ r magnetic susceptibility, χ m Basic Phenomena: Magnetization [C&R §18.2] B = μ H = μ 0 H + μ 0 M In vacuum: B 0 = μ 0 H μ r 0 χ m = μ r 1 μ r , χ m : dimensionless M = m H C&R Figure 18.3 units: A m 4
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Lecture 33, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Units of Basic Magnetic Quantities [C&R §18.2] 5 C&R Table 18.1
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6 Lecture 33, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Units of Basic Magnetic Quantities [C&R §18.2] C&R Table 18.1
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7 Lecture 33, spring 2010 ENGR 145, Chemistry of Materials Case Western Reserve University Magnetization: alignment of magnetic moments in material Magnetic moments are vectors (magnitude & direction) E.g., current I in a circular loop of radius r has magnetic moment m = I π r 2
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This note was uploaded on 01/30/2011 for the course EMSE 103 taught by Professor Ggh during the Spring '10 term at Case Western.

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L33Magnet145s10 - Lecture 33: Magnetic Properties Reading...

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