On the dependence of differential resistance on the critical current taking into account sample overheating

Voltage-current characteristics of the superconducting (Nb-(76-80%) Zr) cold-worked strip samples have been measured for different values of the temperature, magnetic field and the angle between the field direction and the sample plane. The critical current was changed by more than the order of magnitude. The voltage-current characteristics were calculated for different angles taking into account the integration overheating of samples and the hypothesis on the independence of differential resistance on the critical current. A good agreement of the experimental and calculated voltage-current characteristics shows evidence for the validity of the hypothesis (in this case the maximum pinning force is 5x107 dyn/cm3 at T=1.85 K). The problem of stability of the resistive state is considered connected with heat transfer to liquid helium