Gustav
Kirchhoff

Student: Austin Stilwell Class: PHY-151 Instructor: Prof. G.Camilo Lab Date: July 21, 2014 CVCC
For my term paper I decided to research and write about Gustav Kirchhoff. Gustav was the son of a lawyer; he was born and educated in Königsberg, Prussia (now the Russian city Kaliningrad). He graduated from Albertus University in 1847 and soon after married Clara Richelot, the daughter of his mathematics professor. The couple immediately relocated to Berlin, where Kirchhoff had obtained an unpaid teaching position. In 1850, at the unusually young age of 26, he received an appointment as Professor Extraordinaire in Breslau (now Wroclaw), Poland (Gustav Robert Kirchhoff). Gustav is often referred to as the father of electrical currents. I chose to write my paper about Kirchhoff because; I am currently studying electrical engineering technology. A lot of the information that you learn freshman year is based around Kirchhoff’s Laws. In 1845, Kirchhoff became acquainted with Bunsen, who urged him to follow him to Heidelberg, Germany, which he did in 1854. As a professor of physics at the university there, Kirchhoff was very successful, but he did suffer personal adversity when his wife died in 1869, leaving him alone to finish raising their four children, a task made more difficult by a disability that often confined him to a wheelchair or to the use of crutches (Molecular Expressions). Gustav also announced his voltage laws at this time. These laws allowed for the calculation of currents, voltages, and resistances of electrical circuits. Using Kirchhoff’s laws as long as you know two of the three needed pieces of information you can always find the missing one. He used his laws to generalize the equations describing current flow to the case of electrical conductors in three dimensions. Using these generalizations he was able to demonstrate that current flows through a piece of wire without a resistor at the speed of light (Gustav Robert Kirchhoff). Kirchhoff’s important work on thermal radiation was primarily carried out in the late 1850s and early 1860s. In 1859, his studies led him to propose what is commonly referred to as Kirchhoff’s law in thermodynamics. Proven in 1861, this law holds that at thermal static equilibrium, the emissivity of an object or surface is equivalent to its absorbance at any given wavelength and temperature. In the course of his studies of radiation, Kirchhoff coined the term black body to describe a hypothetical perfect radiator that absorbs all incidents light and, therefore, emits all of that light when maintained at a constant temperature in order to preserve equilibrium. In 1854, Kirchhoff was appointed a position as the professor of physics at the University of Heidelberg thanks to his good friend Robert Bunsen. Once he arrived at Heidelberg he and Bunsen began working and studying with one another. Together they founded spectrum analysis. This demonstrated that every element gives off a characteristic colored light when heated to incandescence. The light, when separated by a prism, has a pattern of individual wavelengths specific for each element. Using this method together they were able to discover two elements, Cesium which was discovered in 1860 and Rubidium which was discovered a year later in 1861(Kirchhoff's Spectroscope). These elements were named after the red and blue lines that appeared in their spectra. Kirchhoff later applied spectrum analysis to the composition of the sun. In an experiment of extraordinary delicacy, Kirchhoff brought the light from both the sun and a flame to the slit at the front of his spectroscope, and then introduced salt into the flame. The bright lines from the flame lined up exactly with the dark lines of the sun – emission and absorption were conjugate processes. There could be only one conclusion – the sun and stars were made of the same atoms as the everyday world (Molecular Expressions). He discovered that when light passes through gas, the gas absorbs those wavelengths that it would normally emit if heated. He used this discovery to explain the numerous dark lines (Fraunhofer Lines) in the sun’s spectrum. When the visible light from below the Sun's surface passes through the layers above it (the photosphere and chromosphere), some of the light at particular wavelengths is absorbed by atoms and ions and so is missing in the spectrum we see. When there is no light it appears as black in the spectrum. This was a huge discovery in astrology (The Fraunhofer).

1."The Fraunhofer Spectrum." The Fraunhofer Spectrum. N.p., n.d. Web. 15 July 2014.

2."Molecular Expressions: Science, Optics and You - Timeline - Gustav Robert Kirchhoff." Molecular Expressions: Science, Optics and You - Timeline - Gustav Robert Kirchhoff. N.p., n.d. Web. 15 July 2014.

3."Kirchhoff's Spectroscope." RSC RSS. N.p., n.d. Web. 16 July 2014.

4.The Editors of Encyclopædia Britannica. "Gustav Robert Kirchhoff (German Physicist)." Encyclopedia Britannica Online. Encyclopedia Britannica, n.d. 16 July 2014.