Question: A straight cylindrical wire lying along the x axis has a length L and a diameter d. It is made of a material that obeys Ohm's law with a resistivity %. Assume that potential V is maintained at x = 0, and that the potential is zero at x = L. In terms of L, d, V, %, and physical constants, derive expressions for
(a) The electric field in the wire,
(b) The resistance of the wire,
(c) The electric current in the wire, and
(d) The current density in the wire. Express vectors in vector notation.
(e) Prove that E = p J.