Direct current I flows through a circuit consisting of a resistor with resistance R, a long coil of radius r2 with dense winding (linear density of turns n) and a straight wire of radius r1 coaxial with the coil (figure). Neglecting the resistance of the coil and wire, find the axial Sz and azimuthal Sj components of the Poynting vector inside the coil far from its ends. Also find the total energy flow through the cross section of the coil.

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