A long straight wire of resistance R, radius a and length l carries a constant current I. The poynting vector for the wire will be

Electric field, E=Vl=IRl (R = Resistance of wire)Magnetic field at the surface of wire, B=μ0I2πa (a = radius of wire)Hence, poynting vector, directed radially inward is given by S=EBμ0=IRμ0l⋅μ0I2πa=I2R2πal