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Gustav Robert Kirchhoff (; 12 March 1824 – 17 October 1887) was a German
physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...
who contributed to the fundamental understanding of
electrical circuit An electrical network is an interconnection of electrical components (e.g., batteries, resistors, inductors, capacitors, switches, transistors) or a model of such an interconnection, consisting of electrical elements (e.g., voltage source ...
s,
spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter ...
, and the emission of black-body
radiation In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
by heated objects. He coined the term
black-body radiation Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific, continuous spe ...
in 1862. Several different sets of concepts are named "Kirchhoff's laws" after him, concerning such diverse subjects as black-body radiation and spectroscopy, electrical circuits, and thermochemistry. The Bunsen–Kirchhoff Award for spectroscopy is named after him and his colleague, Robert Bunsen.


Life and work

Gustav Kirchhoff was born on 12 March 1824 in
Königsberg Königsberg (, ) was the historic Prussian city that is now Kaliningrad, Russia. Königsberg was founded in 1255 on the site of the ancient Old Prussian settlement ''Twangste'' by the Teutonic Knights during the Northern Crusades, and was ...
,
Prussia Prussia, , Old Prussian: ''Prūsa'' or ''Prūsija'' was a German state on the southeast coast of the Baltic Sea. It formed the German Empire under Prussian rule when it united the German states in 1871. It was ''de facto'' dissolved by an e ...
, the son of Friedrich Kirchhoff, a lawyer, and Johanna Henriette Wittke. His family were
Lutherans Lutheranism is one of the largest branches of Protestantism, identifying primarily with the theology of Martin Luther, the 16th-century German monk and reformer whose efforts to reform the theology and practice of the Catholic Church launched ...
in the
Evangelical Church of Prussia The Prussian Union of Churches (known under multiple other names) was a major Protestant church body which emerged in 1817 from a series of decrees by Frederick William III of Prussia that united both Lutheran and Reformed denominations in Pru ...
. He graduated from the Albertus University of Königsberg in 1847 where he attended the mathematico-physical seminar directed by Carl Gustav Jacob Jacobi,
Franz Ernst Neumann Franz Ernst Neumann (11 September 1798 – 23 May 1895) was a German mineralogist, physicist and mathematician. Biography Neumann was born in Joachimsthal, Margraviate of Brandenburg, near Berlin. In 1815 he interrupted his studies at Berlin ...
and Friedrich Julius Richelot. In the same year, he moved to
Berlin Berlin ( , ) is the capital and largest city of Germany by both area and population. Its 3.7 million inhabitants make it the European Union's most populous city, according to population within city limits. One of Germany's sixteen constitu ...
, where he stayed until he received a professorship at Breslau. Later, in 1857, he married Clara Richelot, the daughter of his mathematics professor Richelot. The couple had five children. Clara died in 1869. He married Luise Brömmel in 1872. Kirchhoff formulated his circuit laws, which are now ubiquitous in
electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...
, in 1845, while still a student. He completed this study as a seminar exercise; it later became his doctoral dissertation. He was called to the
University of Heidelberg } Heidelberg University, officially the Ruprecht Karl University of Heidelberg, (german: Ruprecht-Karls-Universität Heidelberg; la, Universitas Ruperto Carola Heidelbergensis) is a public research university in Heidelberg, Baden-Württemberg, ...
in 1854, where he collaborated in spectroscopic work with Robert Bunsen. In 1857, he calculated that an electric signal in a resistanceless wire travels along the wire at the
speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant that is important in many areas of physics. The speed of light is exactly equal to ). According to the special theory of relativity, is the upper limit fo ...
. He proposed his law of thermal radiation in 1859, and gave a proof in 1861. Together Kirchhoff and Bunsen invented the spectroscope, which Kirchhoff used to pioneer the identification of the elements in the Sun, showing in 1859 that the Sun contains
sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...
. He and Bunsen discovered
caesium Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...
and
rubidium Rubidium is the chemical element with the symbol Rb and atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. Rubidium is the first alkali metal in the group to have a density higher ...
in 1861. At
Heidelberg Heidelberg (; Palatine German: ') is a city in the German state of Baden-Württemberg, situated on the river Neckar in south-west Germany. As of the 2016 census, its population was 159,914, of which roughly a quarter consisted of students ...
he ran a mathematico-physical seminar, modelled on Franz Ernst Neumann's, with the mathematician
Leo Koenigsberger Leo or Léo may refer to: Acronyms * Law enforcement officer * Law enforcement organisation * ''Louisville Eccentric Observer'', a free weekly newspaper in Louisville, Kentucky * Michigan Department of Labor and Economic Opportunity Arts a ...
. Among those who attended this seminar were
Arthur Schuster Sir Franz Arthur Friedrich Schuster (12 September 1851 – 14 October 1934) was a German-born British physicist known for his work in spectroscopy, electrochemistry, optics, X-radiography and the application of harmonic analysis to physics. ...
and Sofia Kovalevskaya. He contributed greatly to the field of
spectroscopy Spectroscopy is the field of study that measures and interprets the electromagnetic spectra that result from the interaction between electromagnetic radiation and matter as a function of the wavelength or frequency of the radiation. Matter ...
by formalizing three laws that describe the
spectral ''Spectral'' is a 2016 3D military science fiction, supernatural horror fantasy and action-adventure thriller war film directed by Nic Mathieu. Written by himself, Ian Fried, and George Nolfi from a story by Fried and Mathieu. The film stars J ...
composition of
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
emitted by incandescent objects, building substantially on the discoveries of
David Alter David Alter (December 3, 1807 – September 18, 1881) was a prominent American inventor and scientist of the 19th century. He was born in Westmoreland County, Pennsylvania and graduated from the Reformed Medical School in New York City. He had Ge ...
and Anders Jonas Ångström. In 1862, he was awarded the
Rumford Medal The Rumford Medal is an award bestowed by Britain's Royal Society every alternating year for "an outstandingly important recent discovery in the field of thermal or optical properties of matter made by a scientist working in Europe". First awar ...
for his researches on the fixed lines of the solar spectrum, and on the inversion of the bright lines in the spectra of artificial light. In 1875 Kirchhoff accepted the first chair dedicated specifically to
theoretical physics Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experim ...
at Berlin. He also contributed to
optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultrav ...
, carefully solving the
wave equation The (two-way) wave equation is a second-order linear partial differential equation for the description of waves or standing wave fields — as they occur in classical physics — such as mechanical waves (e.g. water waves, sound waves and ...
to provide a solid foundation for Huygens' principle (and correct it in the process).D. Miller, "Huygens’s wave propagation principle corrected", Opt. Lett. 16, 1370–1372 (1991) In 1864, he was elected as a member of the
American Philosophical Society The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communit ...
. In 1884, he became foreign member of the
Royal Netherlands Academy of Arts and Sciences The Royal Netherlands Academy of Arts and Sciences ( nl, Koninklijke Nederlandse Akademie van Wetenschappen, abbreviated: KNAW) is an organization dedicated to the advancement of science and literature in the Netherlands. The academy is housed ...
. Kirchhoff died in 1887, and was buried in the St Matthäus Kirchhof Cemetery in Schöneberg, Berlin (just a few meters from the graves of the
Brothers Grimm The Brothers Grimm ( or ), Jacob (1785–1863) and Wilhelm (1786–1859), were a brother duo of German academics, philologists, cultural researchers, lexicographers, and authors who together collected and published folklore. They are among th ...
).
Leopold Kronecker Leopold Kronecker (; 7 December 1823 – 29 December 1891) was a German mathematician who worked on number theory, algebra and logic. He criticized Georg Cantor's work on set theory, and was quoted by as having said, "'" ("God made the integers, ...
is buried in the same cemetery.


Kirchhoff's circuit laws

Kirchhoff's first law is that the algebraic sum of currents in a network of conductors meeting at a point (or node) is zero. The second law is that in a closed circuit, the directed sums of the voltages in the system is zero.


Kirchhoff's three laws of spectroscopy

#A solid, liquid, or dense gas excited to emit light will radiate at all wavelengths and thus produce a continuous spectrum. #A low-density gas excited to emit light will do so at specific wavelengths, and this produces an
emission spectrum The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an electron making a transition from a high energy state to a lower energy state. The photon energy of ...
. # If light composing a continuous spectrum passes through a cool, low-density gas, the result will be an absorption spectrum. Kirchhoff did not know about the existence of
energy level A quantum mechanical system or particle that is bound—that is, confined spatially—can only take on certain discrete values of energy, called energy levels. This contrasts with classical particles, which can have any amount of energy. The t ...
s in atoms. The existence of discrete spectral lines was known since Fraunhofer discovered them in 1814. And that the lines formed a discrete mathematical pattern was described by Johann Balmer in 1885.
Joseph Larmor Sir Joseph Larmor (11 July 1857 – 19 May 1942) was an Irish and British physicist and mathematician who made breakthroughs in the understanding of electricity, dynamics, thermodynamics, and the electron theory of matter. His most influen ...
explained the splitting of the
spectral line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to ident ...
s in a
magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
known as the
Zeeman Effect The Zeeman effect (; ) is the effect of splitting of a spectral line into several components in the presence of a static magnetic field. It is named after the Dutch physicist Pieter Zeeman, who discovered it in 1896 and received a Nobel pr ...
by the
oscillation Oscillation is the repetitive or periodic variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. Familiar examples of oscillation include a swinging pendul ...
of electrons. But these discrete spectral lines were not explained as electron transitions until the
Bohr model In atomic physics, the Bohr model or Rutherford–Bohr model, presented by Niels Bohr and Ernest Rutherford in 1913, is a system consisting of a small, dense nucleus surrounded by orbiting electrons—similar to the structure of the Solar Syst ...
of the atom in 1913, which helped lead to
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
.


Kirchhoff's law of thermal radiation

It was
Kirchhoff's law of thermal radiation In heat transfer, Kirchhoff's law of thermal radiation refers to wavelength-specific radiative emission and absorption by a material body in thermodynamic equilibrium, including radiative exchange equilibrium. It is a special case of Onsage ...
in which he proposed an unknown universal law for radiation that led
Max Planck Max Karl Ernst Ludwig Planck (, ; 23 April 1858 – 4 October 1947) was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918. Planck made many substantial contributions to theoretical p ...
to the discovery of the quantum of action leading to
quantum mechanics Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, ...
.


Kirchhoff's law of thermochemistry

Kirchhoff showed in 1858 that, in
thermochemistry Thermochemistry is the study of the heat energy which is associated with chemical reactions and/or phase changes such as melting and boiling. A reaction may release or absorb energy, and a phase change may do the same. Thermochemistry focuses on ...
, the variation of the heat of a chemical reaction is given by the difference in
heat capacity Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin (J/K). Heat cap ...
between products and reactants: :\left(\frac\right)_p = \Delta C_p. Integration of this equation permits the evaluation of the heat of reaction at one temperature from measurements at another temperature.


Works

* * * ''Vorlesungen über mathematische Physik''. 4 vols., B. G. Teubner, Leipzig 1876–1894. ** Vol. 1: ''Mechanik''. 1. Auflage, B. G. Teubner, Leipzig 1876
online
. ** Vol. 2: ''Mathematische Optik''. B. G. Teubner, Leipzig 1891 (Herausgegeben von Kurt Hensel
online
. ** Vol. 3: ''Electricität und Magnetismus''. B. G. Teubner, Leipzig 1891 (Herausgegeben von Max Planck
online
. ** Vol. 4
''Theorie der Wärme''
B. G. Teubner, Leipzig 1894, Herausgegeben von Max Planck


See also

*
Kirchhoff equations In fluid dynamics, the Kirchhoff equations, named after Gustav Kirchhoff, describe the motion of a rigid body in an ideal fluid. : \begin & = \times \vec \omega + \times \vec v + \vec Q_h + \vec Q, \\0pt & = \times \vec \omega + \vec F_h ...
* Kirchhoff integral theorem * Kirchhoff matrix * Kirchhoff stress tensor * Kirchhoff transformation * Kirchhoff's diffraction formula * Kirchhoff's perfect black bodies *
Kirchhoff's theorem In the mathematical field of graph theory, Kirchhoff's theorem or Kirchhoff's matrix tree theorem named after Gustav Kirchhoff is a theorem about the number of spanning trees in a graph, showing that this number can be computed in polynomial ti ...
* Kirchhoff–Helmholtz integral *
Kirchhoff–Love plate theory The Kirchhoff–Love theory of plates is a two-dimensional mathematical model that is used to determine the stresses and deformations in thin plates subjected to forces and moments. This theory is an extension of Euler-Bernoulli beam theory a ...
* Piola–Kirchhoff stress * Saint Venant–Kirchhoff model * Stokes–Kirchhoff attenuation formula * Circuit rank * Computational aeroacoustics * Flame emission spectroscopy * Spectroscope *
Kirchhoff Institute of Physics The Faculty of Physics and Astronomy is one of twelve faculties at the University of Heidelberg. It comprises the Kirchhoff Institute of Physics, the Institute of Physics, Theoretical Physics, Environmental Physics and Theoretical Astrophysics. Ki ...
* List of German inventors and discoverers


Notes


References

* * *
HathiTrust full text
Partial English translation available in Magie, William Francis, ''A Source Book in Physics'' (1963). Cambridge: Harvard UP. p. 354-360.


Further reading

* * * * Klaus Hentschel: Gustav Robert Kirchhoff und seine Zusammenarbeit mit Robert Wilhelm Bunsen, in: Karl von Meyenn (Hrsg.) ''Die Grossen Physiker'', Munich: Beck, vol. 1 (1997), pp. 416–430, 475–477, 532–534. * Klaus Hentschel
''Mapping the Spectrum. Techniques of Visual Representation in Research and Teaching''
Oxford: OUP, 2002.
Kirchhoff's 1857 paper on the speed of electrical signals in a wire
*


External links

* *
Open Library
{{DEFAULTSORT:Kirchhoff, Gustav 1824 births 1887 deaths Optical physicists 19th-century German inventors Discoverers of chemical elements Scientists from Königsberg Spectroscopists Fluid dynamicists University of Königsberg alumni University of Breslau faculty Heidelberg University faculty Humboldt University of Berlin faculty Honorary Fellows of the Royal Society of Edinburgh Foreign Members of the Royal Society Foreign associates of the National Academy of Sciences Members of the Royal Netherlands Academy of Arts and Sciences Recipients of the Pour le Mérite (civil class) 19th-century German physicists Rare earth scientists Fellows of the Royal Society of Edinburgh Recipients of the Matteucci Medal Members of the Göttingen Academy of Sciences and Humanities