Question Details

It is possible to reach a temperature close to 0.01K using the magnetic cooling technique. In this process, a strong magnetic field is imposed on a paramagnetic salt that is kept at 1 K by transferring heat to liquid helium that is boiling at very low pressure. The salt is then thermally isolated from the helium and the magnetic field is removed. Thus, the temperature of the salt decreases. Assuming that 1.5 mJ of energy is removed from the paramagnetic salt at an average temperature of 0.1 K, that the ambient temperature is equal to 290 K and that, in order to establish the theoretical limit, the necessary refrigeration is produced by a refrigeration cycle of Carnot, determine:

a) The work provided to the refrigerator of this refrigeration cycle (J)

b) The coefficient of performance of this refrigeration cycle