CRITICAL CURRENTS IN NORMAL CONDUCTORS

It is shown that in a normal conductor the value of a current that generates a magnetic pressure equal to the critical pressure may be considerably lower than it is generally considered. The lower value of the critical current occurs due to the shift of the whole curve of phase equilibrium in the presence of strong electric current. This shift arises due to the additional work performed against ponderomotive forces which prevents from the formation of the nucleus of a phase with a lower value of electric conductivity. In case of the Van der Waals model of the critical state the value of the critical current calculated taking into account the shift of the phase equilibrium curve is by factor 2-3 less than the critical current determined when this effect is neglected.