Moritz von Jacobi
Encyclopedia
Moritz Hermann von Jacobi (September 21, 1801 – March 10, 1874) was a Jewish German
engineer and physicist born in Potsdam
. Jacobi worked mainly in Russia
. He furthered progress in galvanoplastic
s, electric motor
s, and wire
telegraphy
.
s. In 1835 moved to Dorpat (now Tartu, Estonia) to lecture at Dorpat University
. He moved to Saint Petersburg
in 1837 to research usage of electromagnetic forces for moving machines for Russian Academy of Sciences
. He investigated the power of an electromagnet in motors and generators. While studying the transfer of power from a battery
to an electric motor, he deduced the maximum power theorem
. Jacobi tested motors output by determining the amount of zinc consumed by the battery. With financial assistance of Czar Nicholas, Jacobi constructed in 1839 a 28 foot electric motor boat powered by battery
cells. The boat carried 14 passengers on Neva river against the current. The boat fared at the speed
of three miles for hour.
states:
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. Jacobi obtained his theorem
by common sense
.
. The way in which 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 printing
.
He also worked on the development of the electric telegraph. In 1842-1845 he built a telegraph line between Saint Petersburg
and Tsarskoe Selo using an underground cable. In 1867 he was a Russian delegate to the Commission on measurement units at the Paris
World's Fair
. He was a strong proponent of the metric system
.
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
engineer and physicist born in Potsdam
Potsdam
Potsdam is the capital city of the German federal state of Brandenburg and part of the Berlin/Brandenburg Metropolitan Region. It is situated on the River Havel, southwest of Berlin city centre....
. Jacobi worked mainly in Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
. He furthered progress in galvanoplastic
Electrotyping
Electrotyping 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 other fields...
s, electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
s, and wire
Wire
A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads and to carry electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Standard sizes are determined by various...
telegraphy
Telegraphy
Telegraphy is the long-distance transmission of messages via some form of signalling technology. Telegraphy requires messages to be converted to a code which is known to both sender and receiver...
.
Motors
In 1834 he began to study magnetic motorElectric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
s. In 1835 moved to Dorpat (now Tartu, Estonia) to lecture at Dorpat University
University of Tartu
The University of Tartu is a classical university in the city of Tartu, Estonia. University of Tartu is the national university of Estonia; it is the biggest and highest-ranked university in Estonia...
. He moved to Saint Petersburg
Saint Petersburg
Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...
in 1837 to research usage of electromagnetic forces for moving machines for Russian Academy of Sciences
Russian Academy of Sciences
The Russian Academy of Sciences consists of the national academy of Russia and a network of scientific research institutes from across the Russian Federation as well as auxiliary scientific and social units like libraries, publishers and hospitals....
. He investigated the power of an electromagnet in motors and generators. While studying the transfer of power from a battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
to an electric motor, he deduced the maximum power theorem
Maximum power theorem
In electrical engineering, the maximum power transfer theorem states that, to obtain maximum external power from a source with a finite internal resistance, the resistance of the load must be equal to the resistance of the source as viewed from the output terminals...
. Jacobi tested motors output by determining the amount of zinc consumed by the battery. With financial assistance of Czar Nicholas, Jacobi constructed in 1839 a 28 foot electric motor boat powered by battery
Battery (electricity)
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery in 1800 by Alessandro Volta and especially since the technically improved Daniell cell in 1836, batteries have become a common power...
cells. The boat carried 14 passengers on Neva river against the current. The boat fared at the speed
Speed
In kinematics, the speed of an object is the magnitude of its velocity ; it is thus a scalar quantity. The average speed of an object in an interval of time is the distance traveled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as...
of three miles for hour.
Jacobi's Law
The law known as the maximum power theoremMaximum power theorem
In electrical engineering, the maximum power transfer theorem states that, to obtain maximum external power from a source with a finite internal resistance, the resistance of the load must be equal to the resistance of the source as viewed from the output terminals...
states:
- "Maximum power is transferred when the internal resistance 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. Jacobi obtained his theorem
Theorem
In mathematics, a theorem is a statement that has been proven on the basis of previously established statements, such as other theorems, and previously accepted statements, such as axioms...
by common sense
Common sense
Common sense is defined by Merriam-Webster as, "sound and prudent judgment based on a simple perception of the situation or facts." Thus, "common sense" equates to the knowledge and experience which most people already have, or which the person using the term believes that they do or should have...
.
Electrotyping and telegraphy
In 1838, he discovered galvanoplastics, or electrotyping, a method of making printing plates by electroplatingElectroplating
Electroplating is a plating process in which metal ions in a solution are moved by an electric field to coat an electrode. The process uses electrical current to reduce cations of a desired material from a solution and coat a conductive object with a thin layer of the material, such as a metal...
. The way in which this works is analogous to a battery acting in reverse. The stereotype
Stereotype
A stereotype is a popular belief about specific social groups or types of individuals. The concepts of "stereotype" and "prejudice" are often confused with many other different meanings...
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 printing
Relief print
A relief print is an image created by a printmaking process where protruding surface faces of the matrix are inked; recessed areas are ink free. Printing the image is therefore a relatively simple matter of inking the face of the matrix and bringing it in firm contact with the paper...
.
He also worked on the development of the electric telegraph. In 1842-1845 he built a telegraph line between Saint Petersburg
Saint Petersburg
Saint Petersburg is a city and a federal subject of Russia located on the Neva River at the head of the Gulf of Finland on the Baltic Sea...
and Tsarskoe Selo using an underground cable. In 1867 he was a Russian delegate to the Commission on measurement units at the Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
World's Fair
World's Fair
World's fair, World fair, Universal Exposition, and World Expo are various large public exhibitions held in different parts of the world. The first Expo was held in The Crystal Palace in Hyde Park, London, United Kingdom, in 1851, under the title "Great Exhibition of the Works of Industry of All...
. He was a strong proponent of the metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
.
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