Assignment:
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.
Provide complete and step by step solution for the question and show calculations and use formulas.