Rudolf Clausius

Rudolf Julius Emanuel Clausius ( January 2, 1822 in Koszalin, † August 24, 1888 in Bonn ) was a German physicist.

Clausius considered as the discoverer of the second law of thermodynamics, entropy and creator of the virial terms, as well as one of the first theoretical physicist in the middle of the 19th century. He was a contemporary of Helmholtz, Joule, Kirchhoff, Kelvin, Loschmidt, Boltzmann and Maxwell.

Life

The son of a school board and pastor Clausius studied after completion of the Gymnasium in Stettin from 1840 in Berlin mathematics and physics, among others, Heinrich Gustav Magnus, Peter Gustav Lejeune Dirichlet, Jakob Steiner and history with Leopold von Ranke. In 1847 he received his doctorate in hall at Johann Salomo Christoph Schweigger via optical effects in the atmosphere to the doctor of philosophy. By 1850, he was then on Friedrichswerder Gymnasium in Berlin working as a teacher of physics and mathematics. He then became professor of physics at the Royal Artillery and Engineering School in Berlin and a lecturer at the Berlin University. In 1855 he went to the newly established Federal Institute of Technology in Zurich in 1867, he moved to Würzburg and then 1869 until his death in Bonn.

As the leader of a student's medical corps, he was wounded in 1870 in German -Prussian War, which caused constant pain in the knee.

His first wife died giving birth to their sixth child in 1875. Daughter Mathilde, who kept house for him and since then had taken over the education of siblings, married in 1882 the theologian Friedrich room. Two years before his death married Clausius again.

Work

After the discovery of conservation of energy ( first law of thermodynamics ) by Mayer, Joule and Helmholtz had a new theory of heat to be found, especially since Thomson ( later Lord Kelvin) had clearly shown that between Carnot process and the conservation of energy was a contradiction. This task was dedicated to Clausius, by subjecting the ability of heat to convert into work, a detailed study ( 1850). He recorded it for the first time the 2nd law of thermodynamics, which states that heat goes not without other changes from a cold to a warmer body and thus the impossibility of a perpetual motion machine of the second kind in 1865 led Clausius the concept of entropy. This is also the now obsolete unit Clausius was used.

Clausius ' first scientific work deals with issues of meteorological optics, such as the formation of rainbows or the phenomenon of blue sky. His famous treatise "On the motive power of heat " in 1850 enabled him eventually to teach at the Royal Artillery and Engineering School and at the same time as a lecturer at the University of Berlin - his scientific career starts.

Clausius ' name is first brought directly to the Clausius -Clapeyron equation in conjunction with the help of the vapor pressure curve can be determined in two-phase diagram of a substance from the vaporization enthalpy, temperature and volume increase. By the Rankine process, the classical water -vapor process for producing mechanical energy or electricity from chemically bonded heat, he is also known in energy technology. Today is far less common that it has provided fundamental work on the kinetic theory of gases and electrolytic dissociation. In 1857 he refined August Carl Krönigs very simple gas- kinetic model, the latter has previously set a year, and introduces the concept of the " mean free path " of a gas molecule. Its also translated into English works this has led James Clerk Maxwell and Ludwig Boltzmann later to crucial discoveries that explain the kinetic theory of gases significantly. Last but not least Clausius also worked on a Electrodynamics of Moving Bodies, which has yet to be found by Einstein's work in 1905 their solution. Clausius used the derivatives of Maxwell for the determination of the molar refraction of a substance ( Clausius- Mosottische equation). This method was used to verify the structure of an organic substance. From the refractive index and the molar mass of the structures (functional groups, bonds) can be compared by organic molecules.

In 1850 Clausius began to deal with the art to which he owes his greatest fame: the mechanical theory of heat (thermodynamics ). Clausius took of Sadi Carnot 1824 forethought and finally in 1842 postulated by Julius Robert Mayer principle of conservation of energy as the first law of thermodynamics in its theory and gave him the first quantitative formulation by 1850 a relationship between the amount of heat Q, work W and internal energy U aufstellte (dU = dQ dW ). In contrast to the hitherto prevailing opinion, he realized that heat is not an unchanging substance, but represents only one form of energy ( kinetic energy, etc. ) can be converted into the other known forms.

However, the conservation of energy principle does not explain the common fact that energy conversion does not take place in any direction: for example, why two different warm body to align with their contact temperatures, but never passes heat by itself from the colder to the warmer body. Already Carnot had clearly stated this fact, but only recognizes Clausius behind a flow of energy and not a bound on a caloric phenomenon. In 1850, he described this experience as the Second Law of Thermodynamics. The finding that irreversible energy conversions run in one direction, is no longer compatible with the classic mechanical physics, the linear laws according to any process traceable and reversible ( reversible) is ( Poincaré recurrence theorem ).

The first thing to Carnot as well as Clausius ' was the operation of steam engines. Already in 1824 Carnot had found that heat is not completely into mechanical work mutable, because this is not only a source of heat (fire room with steam generator ), but also a heat sink ( condenser for steam condensation ) is required, in which a portion of the thermal conversion work will be lost. Each thermal power process requires two heat reservoirs at different temperatures, from each of which heat is supplied and removed. Under idealized, that is reversible conditions, the ratios of plus or dissipated heat to the respective temperatures at which place the heat transfer, the same. In this case, from the cyclic process a maximum amount of mechanical energy, for example, for power generation, can be obtained. In real thermal power processes, this is not the case. The greater the difference between these conditions, the less useful work ( exergy ) can be obtained from the thermal energy.

The change of the specific heat of the transition temperature heat in a thermodynamic process is thus a measure of the convertibility of heat and mechanical power, and thus of the quality of the process ( DS = dQ / T). This " equivalent value of transformation " called Clausius later " entropy " ( from ancient Greek: = entrepein convert and Trope = conversion potential ). Helmholtz will define 1882 Clausius ' entropy law illustrative of the internal energy of a system: The maximum usable free energy in an isolated system is always less than the actual, internal energy. Although obtained from the conversion into useful work, the internal energy of the system remains ( 1st law ), it is devalued (degradation), as well as becoming a part in the system environment scattered ( dissipated ) is. Thus, the second law of thermodynamics can also be formulated as follows: An energy conversion never runs by itself from a state of low quality to a state of high quality; the entropy increases always. In combined heat and power process must be "refined " by external supply of heat ( firing ) the process medium water energy by water vapor is formed under high pressure and temperature before it can afford in the cylinder of the steam engine or the turbine work to generate electricity. The energy of the processed steam is worthless and must be submitted via the radiator into the environment. Even under ideal conditions, would be the production of energy dissipated as waste heat, inevitable.

Due to the importance of the knowledge of Clausius for the classic Wärmkraftwerkprozess ( Rankine cycle ) this is also called the Rankine process.

1870 was Clausius the virial, which is a relationship between the time average of the kinetic energy and the time average of the potential energy of a closed stationary physical system. He therefore has relation to mechanics and to a closed thermodynamic system.

"The importance of thermodynamic rates for our knowledge of nature has Helmholtz occasionally characterized by predicting it would be world law ' referred to, apparently to express so [ ... ] that you can apply them harmless even to the whole universe ," said Walther Nernst 1922, from a commemorative event to mark the 100th birthday of Clausius in the University of Bonn.

Honors and Memberships (Selection)

• Honorary Doctorate of Medicine, University of Würzburg
• Copleymedaille
• Foreign Member of the Accademia Nazionale dei Lincei in Rome in 1880
• Member of the Leopoldina in 1880
• Order Pour le Mérite for Arts and Sciences in 1888

In addition, the lunar crater Clausius was named after him in 1935.

Since 2009, recalls in his home town of Koszalin, a memorial stone at him.