Question

Simple exam ple o f therm al interaction Consider the system of spins described in Table 3.3. Suppose that, when the systems A and A ' are initially separated from each other, measurements show the total magnetic moment of A to be —3{io and the total magnetic moment of A ' to be +4jj.0. The systems are now placed in thermal contact with each other and are allowed to exchange energy until the final equilibrium situation has been reached. Under these conditions calculate: (ia) The probability P (M ) that the total magnetic moment of A assumes any one of its possible values M. (b) The mean value M of the total magnetic moment of A. (c) Suppose that the systems are now again separated so that they are no longer free to exchange energy with each other. W hat are the values of P(M ) and M of the system A after this separation?