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# Biot, Jean-Baptiste

This article has been reviewed by the following Topic Editor: Tom Lawrence

Jean-Baptiste Biot (1774-1862) was a French mathematician and physicist who is regarded among the founders of the theory of electromagnetism. In 1820, he and physicist Félix Savart discovered that the intensity of the magnetic field set up by a current flowing through a wire is inversely proportional to the distance from the wire. This relationship is now known as the Biot-Savart Law and is fundamental to modern electromagnetic theory. While studying polarized light (light having all of its waves in the same plane), he found that sugar solutions, among others, rotate the plane of polarization when a polarized light beam passes through the solution (1835). This provided a simple method for analyzing sugar solutions and laid the foundation for the fields of polarimetry and saccharimetry. For this work, Biot was awarded the Rumford Medal of the Royal Society in 1840. Biot also accompanied J.L. Gay-Lussac on the first balloon flight for scientific purposes. While testing upper atmospheric composition, they found that the Earth's magnetic field does not vary noticeably with altitude.

In the field of heat transfer, an important dimensionless parameter is named for J.P. Biot. The Biot number is considered when both internal conduction and external convection are involved, and is particularly used for transient heat transfer analysis of a solid object. It is the ratio of the internal thermal conduction resistance of a solid compared to the external convection boundary layer resistance. The general equation for the Biot number is given as follows.

Bi=(hLc)/k where: h is the boundary convection heat transfer coefficient; L is a characteristic length of the object; and k is the internal conduction heat transfer coefficient.

Pioneers in Optics (Florida State University)
Biot-Savart Law (Georgia State University)

## Citation

Cutler J. Cleveland (Lead Author);Tom Lawrence (Topic Editor) "Biot, Jean-Baptiste". In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). [First published in the Encyclopedia of Earth September 28, 2006; Last revised Date September 28, 2006; Retrieved May 23, 2013 <http://www.eoearth.org/article/Biot,_Jean-Baptiste>

## The Author

Cutler J. Cleveland  is Professor of Earth and Environment at Boston University, where he also is on the faculty of the Center for Energy and Environmental Studies. Professor Cleveland is Editor-in-Chief of the Encyclopedia of Energy (Elsevier, 2004), winner of an American Library Association award, the Dictionary of Energy (Elsevier, 2005), Handbook of Energy (Elsevier, forthcoming), and is the Founding Editor-in-Chief of the Encyclopedia of Earth.  He is the recipient of the Adelma ... (Full Bio)