Moritz Hermann or Boris Semyonovich (von) Jacobi (russian: Борис Семёнович Якоби; 21 September 1801,

Potsdam Potsdam () is the capital and, with around 183,000 inhabitants, largest city of the German state of Brandenburg. It is part of the Berlin/Brandenburg Metropolitan Region. Potsdam sits on the River Havel, a tributary of the Elbe, downstream o ...

– 10 March 1874,

Saint Petersburg Saint Petersburg ( rus, links=no, Санкт-Петербург, a=Ru-Sankt Peterburg Leningrad Petrograd Piter.ogg, r=Sankt-Peterburg, p=ˈsankt pʲɪtʲɪrˈburk), formerly known as Petrograd (1914–1924) and later Leningrad (1924–1991), i ...

) was a

Prussian 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 ...

and

Russian Russian(s) refers to anything related to Russia, including: *Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (), Russian language term for all citizens and peo ...

Imperial engineer and physicist of Jewish descent. Jacobi worked mainly in the

Russian Empire The Russian Empire was an empire and the final period of the Russian monarchy from 1721 to 1917, ruling across large parts of Eurasia. It succeeded the Tsardom of Russia following the Treaty of Nystad, which ended the Great Northern War. ...

. He furthered progress in

galvanoplastic Electrotyping (also galvanoplasty) is a chemical method for forming metal parts that exactly reproduce a model. The method was invented by Moritz von Jacobi in Russia in 1838, and was immediately adopted for applications in printing and several o ...

electric motor An electric motor is an electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a wire winding to generate for ...

s, and

wire Overhead power cabling. The conductor consists of seven strands of steel (centre, high tensile strength), surrounded by four outer layers of aluminium (high conductivity). Sample diameter 40 mm A wire is a flexible strand of metal. Wire is c ...

telegraphy Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas ...

Motors

Born into an Ashkenazi Jewish family, Jacobi began to study magnetic motors in 1834. In 1835 moved to

Dorpat Tartu is the second largest city in Estonia after the Northern European country's political and financial capital, Tallinn. Tartu has a population of 91,407 (as of 2021). It is southeast of Tallinn and 245 kilometres (152 miles) northeast of ...

(now Tartu, Estonia) to lecture at Dorpat University. He moved to

in 1837 to research the usage of

electromagnetic force In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions o ...

s for moving machines at the

Russian Academy of Sciences The Russian Academy of Sciences (RAS; russian: Росси́йская акаде́мия нау́к (РАН) ''Rossíyskaya akadémiya naúk'') consists of the national academy of Russia; a network of scientific research institutes from across ...

. He investigated the power of an electromagnet in motors and generators. While studying the transfer of power from a

battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...

to an electric motor, he deduced the

maximum power theorem In electrical engineering, the maximum power transfer theorem states that, to obtain ''maximum'' external power from a power source with internal resistance, the resistance of the load must equal the resistance of the source as viewed from its o ...

. Jacobi tested the output of motors by determining the amount of zinc consumed by the battery. With the financial assistance of Czar Nicholas, in 1839 Jacobi constructed a 28-foot electric motor boat powered by

cells, which carried 14 passengers on the

Neva The Neva (russian: Нева́, ) is a river in northwestern Russia flowing from Lake Ladoga through the western part of Leningrad Oblast (historical region of Ingria) to the Neva Bay of the Gulf of Finland. Despite its modest length of , it ...

river against the current at three miles per hour.

Jacobi's law

''Circuit Diagram''
Power is being transferred from the source,
with

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...

''V'' and resistance ''R_S'',
to a load with resistance ''R_L'',
resulting in a current ''I''. ''I'' is simply
the source voltage divided by the total
circuit resistance

The law known as the

states: : "Maximum power is transferred when the

internal resistance A practical electrical power source which is a linear electric circuit may, according to Thévenin's theorem, be represented as an ideal voltage source in series with an impedance. This impedance is termed the internal resistance of the source. ...

of the source equals the resistance of the load, when the external resistance can be varied, and the internal resistance is constant." The transfer of maximum power from a source with a fixed internal resistance to a load, the resistance of the load must be the same as that of the source. This law is of use when driving a load such as an electric motor from a battery.

Electrotyping and telegraphy

In 1838, he discovered galvanoplastics, or electrotyping, a method of making printing plates by electroplating. The way this works is analogous to a battery acting in reverse. The '' stereotype'' was an impression taken from a form of movable lead type and used for printing instead of the original type. This technique is used in

relief print Relief printing is a family of printing methods where a printing block, plate or matrix, which has had ink applied to its non-recessed surface, is brought into contact with paper. The non-recessed surface will leave ink on the paper, whereas t ...

ing. He also worked on the development of the

electric telegraph Electrical telegraphs were point-to-point text messaging systems, primarily used from the 1840s until the late 20th century. It was the first electrical telecommunications system and the most widely used of a number of early messaging systems ...

. In 1842-1845 he built a telegraph line between

and

Tsarskoe Selo Tsarskoye Selo ( rus, Ца́рское Село́, p=ˈtsarskəɪ sʲɪˈlo, a=Ru_Tsarskoye_Selo.ogg, "Tsar's Village") was the town containing a former residence of the Russian imperial family and visiting nobility, located south from the c ...

using an underground cable. In 1867 he was a Russian delegate to the Commission on Measurement Units at the Paris

World's Fair A world's fair, also known as a universal exhibition or an expo, is a large international exhibition designed to showcase the achievements of nations. These exhibitions vary in character and are held in different parts of the world at a specif ...

. He was a strong proponent of the

metric system The metric system is a system of measurement that succeeded the decimalised system based on the metre that had been introduced in France in the 1790s. The historical development of these systems culminated in the definition of the Interna ...

Naval mine

In 1853, Jacobi developed the Jacobi naval mine. The mine was tied to the sea bottom by an anchor, a cable connected it to a

galvanic cell A galvanic cell or voltaic cell, named after the scientists Luigi Galvani and Alessandro Volta, respectively, is an electrochemical cell in which an electric current is generated from spontaneous Oxidation-Reduction reactions. A common apparatus ...

which powered it from the shore, the power of its explosive charge was equal to of black powder. Its production was approved by the Committee for Mines of the

Ministry of War of the Russian Empire Ministry of War of the Russian Empire, (russian: Военное министерство, ''Military Ministry'') was an administrative body in the Russian Empire from 1802 to 1917. It was established in 1802 as the ''Ministry of ground armed for ...

and in 1854 60 Jacobi mines were laid in the vicinity of the Forts Pavel and

Alexander Alexander is a male given name. The most prominent bearer of the name is Alexander the Great, the king of the Ancient Greek kingdom of Macedonia who created one of the largest empires in ancient history. Variants listed here are Aleksandar, Al ...

(

Kronstadt Kronstadt (russian: Кроншта́дт, Kronshtadt ), also spelled Kronshtadt, Cronstadt or Kronštádt (from german: link=no, Krone for " crown" and ''Stadt'' for "city") is a Russian port city in Kronshtadtsky District of the federal city ...

Family

Von Jacobi's brother was the mathematician

Carl Gustav Jacob Jacobi Carl Gustav Jacob Jacobi (; ; 10 December 1804 – 18 February 1851) was a German mathematician who made fundamental contributions to elliptic functions, dynamics, differential equations, determinants, and number theory. His name is occasiona ...

Notes

External links

* * Calvert, J. B., "
Jacobi's Theorem
Also known as the Maximum Power Transfer Theorem, misunderstanding of it retarded development of dynamos''". March 30, 2001

Jacobi's motor - The first real electric motor of 1834 {{DEFAULTSORT:Jacobi, Moritz von 1801 births 1874 deaths German Ashkenazi Jews German emigrants to the Russian Empire Engineers from the Russian Empire Russian electrical engineers Inventors from the Russian Empire Demidov Prize laureates Full members of the Saint Petersburg Academy of Sciences Burials at Smolensky Lutheran Cemetery 19th-century engineers from the Russian Empire Sustainable transport pioneers