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Unformatted text preview: The Poynting vector: power and energy in electromagnetic fields Kenneth H. Carpenter Department of Electrical and Computer Engineering Kansas State University October 19, 2004 1 Conservation of energy in electromagnetics The concept of conservation of energy (along with conservation of momen tum ) is one of the basic principles of physics – both classical and modern. When dealing with electromagnetic fields a way is needed to relate the con cept of energy to the fields. This is done by means of the Poynting vector: P = E × H. (1) In eq.(1) E is the electric field intensity, H is the magnetic field intensity, and P is the Poynting vector, which is found to be the power density in the electromagnetic field. The conservation of energy is then established by means of the Poynting theorem. 2 The Poynting theorem By using the Maxwell equations for the curl of the fields along with Gauss’s divergence theorem and an identity from vector analysis, we may prove what is known as the Poynting theorem ....
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 Spring '10
 1
 Conservation Of Energy, Energy, Power, Flux, Energy density, Poynting vector

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