Biography of Johann Christian Poggendorff

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Poggendorff studied problems in electricity and magnetism, he developed a mirror galvanometer and, actually, he gave the name “galvanometer” to a physical instrument measuring an electric current.

Poggendorff was German physicist and chemist. Professor of chemistry at the University of Berlin from 1834, he investigated problems in electricity and magnetism.

In the same year (1826) as Nobili constructed his new galvanometer, Poggendorff invented a method of reading a galvanometer scale by means of a mirror – he designed a mirror galvanometer. Poggendorff built a system in which he installed a small flat mirror to reflect a relatively narrow beam of light.

This apparatus, with the aid of an eyeglass, can be used to measure the torsion angle of the wire suspended from the bar or magnetic needle, when it is under the influence of the electrical current of the conductor. Actually, Poggendorff invented name “galvanometer” for the instrument detecting an electric current to honour Galvani (1737-98) who in fact was unaware of the magnetic effect.

The design of a mirror galvanometer comprises a coil of wire wound on a soft iron core suspended in the magnetic field of a permanent magnet – this coil is suspended generally by means of a strip of phosphor bronze wire and located centrally between the poles of the permanent magnet. The coil will react to a coupling force the extent of which is proportional to the current flowing through the coil, and this will cause the coil to rotate. A small mirror is attached to the coil so that a beam of light reflected by this mirror will sweep through an angle which is proportional to the current passing through the coil.

He founded (1824) and edited the important “Annalen der Physik und Chemie” and edited the first two volumes (1863) of “Biographisch-literarisches Handworterbuch”.

In 1860, J. C. Poggendorf, the editor of a journal of physics andchemistry, received a monograph from Zollner describing his illusion. Poggendorff noticed and described another effect of the apparent misalignment of the diagonal lines in Zollner’s figure. Thus the Poggendorff illusion was discovered. The two segments of the diagonal line appear to be slightly offset in this figure. But it is a straight line !!!

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