## Entropy Sentence Examples

- In the special case of a substance isolated from external heat supply, dH=o, the change of
**entropy**is zero in a reversible process, but must be positive if the process is not reversible. - If we write h=sot+dh, where so is a selected constant value of the specific heat of the liquid, and dh represents the difference of the actual value of h at t from the ideal value sot, and if we similarly write q5 = sologe(6/90)+dcp for the
**entropy**of the liquid at t, where do represents the corresponding difference in the**entropy**(which is easily calculated from a table of values of h), it is shown by Callendar (Proc. R.S. - The adiabatics are lines of constant
**entropy**, and are also called Isentropics. - In the case of an ideal gas, dp/d9 at constant volume =R/v, and dvld6 at constant pressure =R/p; thus we obtain the expressions for the change of
**entropy**0-4)0 from the state poeovo to the state pev, log e e/eo+R logev/vo =S log e 9/00-R (32) In the case of an imperfect gas or vapour, the above expressions are frequently employed, but a more accurate result may be obtained by employing equation (17) with the value of the specific heat, S, from (29), which gives the expression 4-¢o = Sologe0/00 - R logep/po-n(cp/B-copo/Bo) - (33) The state of a substance may be defined by means of the temperature and
**entropy**as co-ordinates, instead of employing the pressure and volume as in the indicator diagram. - Changes of
**entropy**must be calculated in terms of quantities of heat, and must be interpreted in a similar manner. - In practice, however, there is always some frictional dissipation, accompanied by an increase of
**entropy**and by a fall of pressure. - The
**entropy**tends to a maximum, and the state is one of stable equilibrium when the value of the**entropy**is the maximum value consistent with the conditions of the problem. - Since the condition of heat-isolation is impracticable, the condition of maximum
**entropy**cannot, as a rule, be directly applied, and it is necessary to find a more convenient method of expression. - If 0', E', v'; and 4)", E", v", refer to unit mass of the substance in the first and second states respectively in equilibrium at a temperature 0 and pressure p, the heat absorbed, L, per unit mass in a change from the first to the second state is, by definition of the
**entropy**, equal to 0(4)"-4)'), and this by the first law is equal to the change of intrinsic energy, E" - E', plus the external work done, p(v" - v'), i.e. - Writing formulae (3r) and (33) for the energy and
**entropy**with indeterminate constants A and B, instead of taking them between limits, we obtain the following expressions for the thermodynamic functions in the case of the vapour: " =Solog e 0 - R log e p - ncp/D+A". - 0,
**Entropy**of vapour or liquid. - In passing along an adiabatic there is no change of
**entropy**, since no heat is absorbed. - (29) (30) The expression for the change of
**entropy**between any two states is found by dividing either of the expressions for dH in (8) by 0 and integrating between the given limits, since dH/B is a perfect differential. - The 0, 4) diagram is useful in the study of heat waste and condensation, but from other points of view the utility of the conception of
**entropy**as a " factor of heat " is limited by the fact that it does not correspond to any directly measurable physical property, but is merely a mathematical function arising from the form of the definition of absolute temperature. - In all such cases there is necessarily, by Carnot's principle, a loss of efficiency or available energy, accompanied by an increase of
**entropy**, which serves as a convenient measure or criterion of the loss. - If the change is not reversible, but the final state is the same, the change of
**entropy**, do, is the same, but it is no longer equal to dII/B. - The
**entropy**cannot diminish. - The total
**entropy**of the system is found by multiplying the**entropy**per unit mass of the substance in each state by the mass existing in that state, and adding the products so obtained.