Tantalum may be converted from a type I to a type II superconductor when small amounts of interstitial impurities are present. The resistance of type I and type II wire specimens was measured in a transverse magnetic field during the superconducting to normal transition. It was found that for both types carrying a transport current, the resistance for the major portion of the transition region is a function of the Lorentz force acting on the normal domains of the intermediate state or on the flux filaments of the mixed state. The effects of strain and impurity were also studied and were interpreted in terms of their influence in retarding the motion or pinning of normal domains in the material.