Are the earth and sun in thermal equilibrium? Are there entropy changes associated with the transmission of energy from the sun to the earth? Does radiation differ from other modes of heat transfer with respect to entropy changes? Explain your reasoning.
Solution 19D Introduction Here, here at first we have to see whether earth and sun system are in thermal equilibrium. Then we have to describe if there is any change in entropy in the heat process of heat transfer from sun to earth. Then we have to describe whether radiation, in terms of entropy change, is same or different. Step 1 Two object are said to be in thermal equilibrium, if not heat is flowing from one object to another. Now as we know that we receive energy from sun as the form of radiation. Hence we can say that the sun and earth are not in thermal equilibrium. Step 2 The entropy change is defined by Q S = T Where Q is the heat received by the reservoir and T is the temperature of the reservoir. If the energy flows into the reservoir then the change in positive. Now as we know that the energy flows out from the sun and flows into the earth. Hence the total entropy change is S se= Q Q Te Ts Since T e T ,sthe entropy change is not zero and the change is positive. So there is entropy change associated with the flows of energy from sun to earth.