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Boris Jacobi
Moritz Hermann von Jacobi (; 21 September 1801 – 10 March 1874), also known as Boris Semyonovich Yakobi (), was a German-Russian electrical engineer and physicist. Motors Jacobi began to study magnetic motors in 1834. In 1835 moved to Dorpat (now Tartu, Estonia) to lecture at Dorpat University. He moved to Saint Petersburg in 1837 to research the usage of electromagnetic forces for moving machines at the 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 the output of motors by determining the amount of zinc consumed by the battery. With the financial assistance of Tsar Nicholas I, in 1839 Jacobi constructed a 28-foot electric motor boat powered by battery cells, which carried 14 passengers on the Neva river against the current at three miles per hour. Jacobi's law ''Circuit Diagram'' Power is bei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potsdam
Potsdam () is the capital and largest city of the Germany, German States of Germany, state of Brandenburg. It is part of the Berlin/Brandenburg Metropolitan Region. Potsdam sits on the Havel, River Havel, a tributary of the Elbe, downstream of Berlin, and lies embedded in a hilly morainic landscape dotted with many lakes, around 20 of which are located within Potsdam's city limits. It lies some southwest of Berlin's city centre. The name of the city and of many of its boroughs are of Slavic languages, Slavic origin. Potsdam was a residence of the Prussian kings and the German Emperor until 1918. Its planning embodied ideas of the Age of Enlightenment: through a careful balance of architecture and landscape, Potsdam was intended as "a picturesque, pastoral dream" which would remind its residents of their relationship with nature and reason. The city, which is over 1,000 years old, is widely known for its palaces, its lakes, and its overall historical and cultural significance. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physicist
A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate causes of Phenomenon, phenomena, and usually frame their understanding in mathematical terms. They work across a wide range of Physics#Research fields, research fields, spanning all length scales: from atom, sub-atomic and particle physics, through biological physics, to physical cosmology, cosmological length scales encompassing the universe as a whole. The field generally includes two types of physicists: Experimental physics, experimental physicists who specialize in the observation of natural phenomena and the development and analysis of experiments, and Theoretical physics, theoretical physicists who specialize in mathematical modeling of physical systems to rationalize, explain and predict natural phenomena. Physicists can apply their k ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stereotype (printing)
In printing, a stereotype, stereoplate or simply a stereo, is a solid plate of type metal, cast from a papier-mâché or plaster mould taken from the surface of a forme (printing), forme of type. The mould was known as a ''flong''. Background In the days of set movable sort (typesetting), type, printing involved placing individual letters (also called “sort”) plus other elements (including leading and furniture (typesetting), furniture) into a block called a chase (printing), chase. Cumulatively, this full setup for printing a single page was called a forme (printing), forme. Ink was then applied to the forme, pressed against paper and a printed page was made. This process of creating formes was labour-intensive, costly and prevented printers from using their type, leading, furniture and chases for other work. Furthermore, printers who underestimated demand would be forced to reset the type for subsequent print runs. ... while Nathaniel Hawthorne's publishers assumed that ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Internal Resistance
In electrical engineering, a practical electric power source which is a linear 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. When the power source delivers current, the measured voltage output is lower than the no- load voltage; the difference is the voltage drop (the product of current and resistance) caused by the internal resistance. The concept of internal resistance applies to all kinds of electrical sources and is useful for analyzing many types of circuits. Battery A battery may be modeled as a voltage source in series with a resistance. These types of models are known as equivalent circuit models. Another common model being physiochemical models that are physical in nature involving concentrations and reaction rates. In practice, the internal resistance of a battery is dependent on its size, state of charge, chemical properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Resistance (electricity)
The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels with mechanical friction. The SI unit of electrical resistance is the ohm (), while electrical conductance is measured in siemens (S) (formerly called the 'mho' and then represented by ). The resistance of an object depends in large part on the material it is made of. Objects made of electrical insulators like rubber tend to have very high resistance and low conductance, while objects made of electrical conductors like metals tend to have very low resistance and high conductance. This relationship is quantified by resistivity or conductivity. The nature of a material is not the only factor in resistance and conductance, however; it also depends on the size and shape of an object because these properties are extensive rather than in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage
Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), work needed per unit of Electric charge, charge to move a positive Test particle#Electrostatics, test charge from the first point to the second point. In the SI unit, International System of Units (SI), the SI derived unit, derived unit for voltage is the ''volt'' (''V''). The voltage between points can be caused by the build-up of electric charge (e.g., a capacitor), and from an electromotive force (e.g., electromagnetic induction in a Electric generator, generator). On a macroscopic scale, a potential difference can be caused by electrochemical processes (e.g., cells and batteries), the pressure-induced piezoelectric effect, and the thermoelectric effect. Since it is the difference in electric potential, it is a physical Scalar (physics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neva
The Neva ( , ; , ) 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 is the fourth-largest river in Europe in terms of average discharge (after the Volga, the Danube and the Rhine). The Neva is the only river flowing from Lake Ladoga. It flows through the city of Saint Petersburg, the three smaller towns of Shlisselburg, Kirovsk and Otradnoye, and dozens of settlements. It is navigable throughout and is part of the Volga–Baltic Waterway and White Sea–Baltic Canal. It is the site of many major historical events, including the Battle of the Neva in 1240 which gave Alexander Nevsky his name, the founding of Saint Petersburg in 1703, and the Siege of Leningrad by the German army during World War II. The river played a vital role in trade between Byzantium and Scandinavia. Etymology The earliest people in recorde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Vessel
Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell's equations. Common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others. The presence of either a positive or negative electric charge produces an electric field. The motion of electric charges is an electric current and produces a magnetic field. In most applications, Coulomb's law determines the force acting on an electric charge. Electric potential is the work done to move an electric charge from one point to another within an electric field, typically measured in volts. Electricity plays a central role in many modern technologies, serving in electric power where electric current is used to energise equipment, and in electronics dealing with electrical c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tsar Nicholas I
Nicholas I, group=pron (Russian language, Russian: Николай I Павлович; – ) was Emperor of Russia, List of rulers of Partitioned Poland#Kings of the Kingdom of Poland, King of Congress Poland, and Grand Duke of Finland from 1825 to 1855. He was the third son of Paul I of Russia, Paul I and younger brother of his predecessor, Alexander I of Russia, Alexander I. Nicholas's thirty-year reign began with the failed Decembrist revolt. He is mainly remembered as a reactionary whose controversial reign was marked by geographical expansion, centralisation of administrative policies, and repression of dissent both in Imperial Russia, Russia and among its neighbors. Nicholas had a happy marriage that produced a large family, with all of their seven children surviving childhood. Nicholas's biographer Nicholas V. Riasanovsky said that he displayed determination, singleness of purpose, and an iron will, along with a powerful sense of duty and a dedication to very hard work. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 output terminals. Moritz von Jacobi published the maximum power (transfer) theorem around 1840; it is also referred to as "Jacobi's law". The theorem results in maximum ''power'' transfer from the power source to the load, but not maximum ''efficiency'' of useful power out of total power consumed. If the load resistance is made larger than the source resistance, then efficiency increases (since a higher percentage of the source power is transferred to the load), but the ''magnitude'' of the load power decreases (since the total circuit resistance increases). If the load resistance is made smaller than the source resistance, then efficiency decreases (since most of the power ends up being dissipated in the source). Although the total power ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Battery (electricity)
An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections for powering electrical devices. When a battery is supplying power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons. When a battery is connected to an external electric load, those negatively charged electrons flow through the circuit and reach the positive terminal, thus causing a redox reaction by attracting positively charged ions, or cations. Thus, higher energy reactants are converted to lower energy products, and the free-energy difference is delivered to the external circuit as electrical energy. Historically the term "battery" specifically referred to a device composed of multiple cells; however, the usage has evolved to include devices composed of a single cell. Primary (single-use or "disposable") batteries are used once and discarded, as the electrode mat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
