"[W]e... consider the conversion of work into heat and... the passage of heat from a higher to a lower temperature as positive transformations."
Rudolf Julius Emanuel Clausius was a German physicist and mathematician and is considered one of the central founding fathers of the science of thermodynamics. By his restatement of Sadi Carnot's principle known as the Carnot cycle, he gave the theory of heat a truer and sounder basis. His most important paper, "On the Moving Force of Heat", published in 1850, first stated the basic ideas of the s
"[T]he equivalence-value of the transformation of work into the quantity of heat Q, of the temperature t, may be represented... wherein f(t) is...[the same] function of the temperature... for all cases. When Q is negative... it will indicate that the quantity... transformed... from heat into work."
Rudolf Clausius"This principle, upon which the whole of the following development rests, is... Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time. Everything we know the interchange of heat between two bodies of different temperatures confirms this; for heat everywhere manifests a tendency to equalize existing differences of temperature..."
Rudolf Clausius"[W]e may consider the as well as the whole condition of the body... as determined so soon as its t and v are given. We... make these two magnitudes... independent variables, and... consider the pressure p as well as the quantity U... as functions of these. If... t and v receive the increments dt and dv, the corresponding quantity of exterior work done... during an increment of volume dv will be pdv. Hence... and... we obtain"
Rudolf Clausius"In a similar manner... passage of the quantity of heat Q, from... temperature t1 to the temperature t2 must be proportional to the quantity Q, and... can only depend upon the two temperatures.... expressed bywherein F(t1,t2) is...[the same] function of... temperatures... for all cases, and... must change... sign when... temperatures are interchanged; so..."
Rudolf Clausius"Carnots theorem... brought into agreement with the first fundamental theorem, expresses a relation between... the transformation of heat into work, and the passage of heat from a warmer to a colder body... regarded as... heat at a higher, into heat at a lower temperature. The theorem... may be enunciated... as:—In all cases where a quantity of heat is converted into work, and where the body effecting this transformation... returns to its original condition, another quantity of heat must necessarily be transferred from a warmer to a colder body; and the magnitude of the last quantity of heat, in relation to the first, depends only upon the temperatures of the bodies between which heat passes, and not upon the nature of the body effecting the transformation."
Rudolf Clausius"Theorem of the equivalence of Heat and Work. ...Mechanical work may be transformed into heat, and conversely heat into work, the magnitude of the of the one being always proportional to that of the other."
Rudolf Clausius