Unformatted text preview: The beam ²lls a circular area of radius a that is perpendicular to the z axis. The number of electrons per unit volume is n . Calculate the Poynting vector. What is the power that Fows into or out of a length L of the beam. What is the power converted to or from heat or mechanical energy in the volume. 5) Consider an ohmic conductor of the same geometry as the beam in problem 4. Let the conductor have a uniform current density J e z due to an electric ²eld in the conductor in the z direction such that the potential di³erence for a length L is V and the resistance for length L is R. The current is due to the Fow of free electrons with the usual low drift velocity. Calculate the Poynting vector.What is the power that Fows into or out of a length L of the conductor? What is the power converted to or from heat in the volume? 1...
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 Spring '10
 Blecher
 Charge, Magnetism, Mass, Fundamental physics concepts, free charge, mass density ρ′

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