Suppose the bar in Example 21.5 is disconnected from the hightemperature reservoir and allowed to thermally equilibrate with the lowtemperature reservoir.

(a) Are the changes in the energy and entropy of the bar during this process positive, negative, or zero? 

(b) Is there any change in the entropy of the environment?

(c) Does the sum \(S_{\mathrm{bar}}+S_{\mathrm{env}}\) change?

Example 21.5

A steel bar transfers energy from a thermal reservoir at \(750 \mathrm{~K}\) to one at \(520 \mathrm{~K}\). If the bar transfers \(1.5 \times 10^{6} \mathrm{~J}\) of energy during a certain time interval over which the temperature distribution of the bar does not change, what is the entropy change of the environment?