p2020chap09 - PHYS-2020: General Physics II Course Lecture...

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Unformatted text preview: PHYS-2020: General Physics II Course Lecture Notes Section IX Dr. Donald G. Luttermoser East Tennessee State University Edition 3.3 Abstract These class notes are designed for use of the instructor and students of the course PHYS-2020: General Physics II taught by Dr. Donald Luttermoser at East Tennessee State University. These notes make reference to the College Physics, 9th Edition (2012) textbook by Serway and Vuille. IX. Electromagnetic Radiation (Photons) A. Properties of Electromagnetic (E/M) Radiation. 1. Maxwell showed in 1865 that electric phenomena were related to magnetic phenomena = Maxwells equations (or laws ): a) Electric fields originate on positive charges and terminate on negative charges. The electric field due to a point charge can be determined by applying Coulombs law. vector vector E = epsilon1 . i) This is similar to Gausss law given in Eq. (I-7). ii) = q/V is the electric charge density (charge per unit volume). iii) The del symbol is from vector calculus and is defined by vector x x + y y + z z , in Cartesian coordinates, where is the partial derivative symbol from calculus. iv) The vector operation is called the divergence in higher mathematics it is the dot product of the del operator and the vector in question, here the electric-field vector. b) Magnetic-field lines always form closed loops = they do not begin or end anywhere = there are no magnetic monopoles . Mathematically, this is given by Maxwells IX1 IX2 PHYS-2020: General Physics II equation for the divergence of the B-field: vector vector B = 0 , the zero simply means that there are no magnetic monopoles. c) A varying B-field induces an emf and hence electric ( E ) field = Faradays law re-expressed in Maxwells form: vector vector E =- vector B t . The vector operation is called the curl in higher mathe- matics. Whereas the divergence produces a scalar, the curl produces a vector. d) Magnetic fields are generated by moving charges (or cur- rents) = Amperes law re-expressed in Maxwells form: vector vector B = vector J , where J ( q/t ) is the current density. 2. Maxwells last 2 laws allow electromagnetic waves ( i.e. , radiation) to self-propagate at a velocity of c = 1 epsilon1 = 2 . 99792 10 8 m/s . (IX-1) a) c is called the speed of light , since visible light is a form of electromagnetic radiation. b) An oscillating electric charge produces an E-field that varies in time, which produces a B-field that varies in time, which produces a new E-field that varies in time, Donald G. Luttermoser, ETSU IX3 and so on....
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This note was uploaded on 03/21/2012 for the course PHY 2020 taught by Professor Staff during the Fall '08 term at University of Florida.

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p2020chap09 - PHYS-2020: General Physics II Course Lecture...

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