Alexander Grigorievich Stoletov (; 10 August 1839 – 27 May 1896) was a

Russian Russian(s) may refer to: *Russians (), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *A citizen of Russia *Russian language, the most widely spoken of the Slavic languages *''The Russians'', a b ...

physicist, founder of

electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

, and professor in

Moscow University Moscow State University (MSU), officially M. V. Lomonosov Moscow State University,. is a public research university in Moscow, Russia. The university includes 15 research institutes, 43 faculties, more than 300 departments, and six branches. Al ...

. He was the brother of general Nikolai Stoletov.

Biography

Alexander Stoletov defended his doctoral dissertation in 1872 and became professor at

a year later. After defending his dissertation he became a renowned scientist worldwide. He attended the opening ceremony of the physical laboratory in Cambridge in 1874, and represented Russia at the first World Congress of Electricity in Paris in 1881, where he presented his work on links between electrostatic and electromagnetic values.

Contribution to science

His major contributions include pioneer work in the field of

ferromagnetism Ferromagnetism is a property of certain materials (such as iron) that results in a significant, observable magnetic permeability, and in many cases, a significant magnetic coercivity, allowing the material to form a permanent magnet. Ferromagne ...

and discovery of the laws and principles of the outer

photoelectric effect The photoelectric effect is the emission of electrons from a material caused by electromagnetic radiation such as ultraviolet light. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physi ...

. Achievements of Alexander Stoletov include: Magnetism (1871–1872) * Stoletov was the first to show that with the increase of the magnetic field the magnetic susceptibility of iron grows, but then begins to decrease. * Built the curve of the

magnetic permeability In electromagnetism, permeability is the measure of magnetization produced in a material in response to an applied magnetic field. Permeability is typically represented by the (italicized) Greek letter ''μ''. It is the ratio of the magnetic ...

of ferromagnetics, known as the

Stoletov curve Stoletov curve shows the dependence of the magnetic permeability \chi of ferromagnetics on the intensity of the applied magnetic field ''H''. The curve is named after physicist Aleksandr Stoletov who analyzed in a long series of experiments the ma ...

. * Developed two new methods for measuring magnetic properties of various materials. Photoelectric effect (1888–1891) * Studied the outer

, discovered by Hertz in 1887. Published the results in six works. * Developed quantitative methods for the study of the photoelectric effect. * Discovered the direct proportionality between the intensity of light and the corresponding photo induced current ( Stoletov's law) * Discovered the Stoletov constant which defines the ratio between the intensity of the electric current and the gas pressure under the maximum current. * Built the first

solar cell A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

based on the outer photoelectric effect and estimated the response time of the photoelectric current. * Discovered the decrease of the solar cell's sensitivity with time (fatigue of solar cells). Other * Calculated the proportion between electrodynamic and electrostatic units, producing a value very close to the

speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...

Publications

Important published works of Alexander Stoletov include: * On the Kohlrausch's measurement of the mercury unit of electric resistance; * Sur une méthode pour déterminer le rapport des unités électromagnétiques et électrostatiques; * On the electricity of juxtaposition; * On the critical state of bodies (4 articles); * Actino-electric research; * Ether and electricity; * Essay on the development of our knowledge of gases; * Introduction into acoustics and optics.

References

External links

Alexander Stoletov
at th
Russia InfoCentre
{{DEFAULTSORT:Stoletov Aleksandr Grigorievich 1839 births 1896 deaths People from Vladimir, Russia Physicists from the Russian Empire Inventors from the Russian Empire Electrical engineers from the Russian Empire Imperial Moscow University alumni Academic staff of Moscow State University

Biography

Contribution to science

See also

Publications

References

External links