Resistivity and Hall Effect in Superconducting Nb

The resistive electric field and the Hall field were measured in pure Nb in the mixed state as a function of magnetic field at high current densities and at several temperatures. An analysis of vortex motion in the presence of a pinning force gives that in the limit of high current density the differential resistivities become independent of pinning force. We find that the flux-flow resistivity is proportional to $\frac{B}{H_{c2\mathrm{}}}$ and the Hall resistivity equals $\mathrm{RB}$. It follows that the Hall tangent in the mixed state is constant and equal to its value at $H_{c2\mathrm{}}$.