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Poynting Vector on the surface of current carrying conductor

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A straight conducting wire of circular cross section, radius a, has a resistance R per unit length and carries a constant current I. Find the value and direction of the Poynting vector at the surface of the wire, and hence show that the total power entering the wire per unit length is (I^2)R. By considering the divergence of the poynting vector inside the wire, show that the energy is dissipated uniformly through it's volume.

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Sample Physics Questions

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1. Four long parallel wires each carry a 2.0 A current in the same direction. The wires are parallel to the z-axis, and they pass through the corners of a square of side 5.0 cm positioned in the x-y plane as shown in the diagram.
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2. A small generating station produces 5.0 kA of current at V = 10.0 kV. It must be transmitted with only a 4.0% loss of power, in a transmission line of 130 ohms total resistance. To achieve this, the voltage is changed by a transformer with 24 turns in its primary coil.

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