Linear and nonlinear dynamic response to the penetration of very weak magne
tic fields (of the enter of 10(-2) Oe) into polycrystalline superconductors
ale studied theoretically and experimentally. The results of experiments a
re found to be in satisfactory agreement with the conclusions of the low-fi
eld electrodynamics. (C) 2001 MAIK "Nauka/Interperiodica".