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Dynamo (electrical)
"Dynamo Electric Machine" (end view, partly section, ) A dynamo is an electrical generator that creates direct current using a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter. Today, the simpler alternator dominates large scale power generation, for efficiency, reliability and cost reasons. A dynamo has the disadvantages of a mechanical commutator. Also, converting alternating to direct current using rectifiers (such as vacuum tubes or more recently via solid state technology) is effective and usually economical. History Induction with permanent magnets The Faraday disk was the first electric generator. The horseshoe-shaped magnet ''(A)'' created a magnetic field through the disk ''(D)''. When the disk was turned, this induced an electr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetic Flux
In physics, specifically electromagnetism, the magnetic flux through a surface is the surface integral of the normal component of the magnetic field B over that surface. It is usually denoted or . The SI unit of magnetic flux is the weber (Wb; in derived units, volt–seconds), and the CGS unit is the maxwell. Magnetic flux is usually measured with a fluxmeter, which contains measuring coils and electronics, that evaluates the change of voltage in the measuring coils to calculate the measurement of magnetic flux. Description The magnetic interaction is described in terms of a vector field, where each point in space is associated with a vector that determines what force a moving charge would experience at that point (see Lorentz force). Since a vector field is quite difficult to visualize at first, in elementary physics one may instead visualize this field with field lines. The magnetic flux through some surface, in this simplified picture, is proportional to the nu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Axial Symmetry
Axial symmetry is symmetry around an axis; an object is axially symmetric if its appearance is unchanged if rotated around an axis. glossary of meteorology. Retrieved 2010-04-08. For example, a without trademark or other design, or a plain white tea saucer, looks the same if it is rotated by any angle about the line passing lengthwise through its center, so it is axially symmetric. Axial symmetry can also be [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antonio Pacinotti
Antonio Pacinotti (17 June 1841 – 24 March 1912) was an Italian physicist, who was Professor of Physics at the University of Pisa. Biography Pacinotti was born in Pisa, where he also died. He was the son of Luigi Pacinotti and Caterina Catanti, attended the ''istituto arcivescovile Santa Caterina'', and took part in the second war of Italian independence as ''sergente volontario''. He was a student of Carlo Matteucci and graduated in mathematics at Pisa under Riccardo Felici. He was appointed as assistant to the astronomer Giovanni Battista Donati in 1862, professor at the technological institute of Bologna in 1864, professor of physics at the University of Cagliari in 1873, and, finally, successor to his father in 1881 in the chair of technological physics at the University of Pisa. Among his students was Augusto Righi. Pacinotti died in Pisa. Scientific studies and invention of the dynamo He is best known for inventing an improved form of direct-current electrica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pacinotti Dynamo
Antonio Pacinotti (17 June 1841 – 24 March 1912) was an Italian physicist, who was Professor of Physics at the University of Pisa. Biography Pacinotti was born in Pisa, where he also died. He was the son of Luigi Pacinotti and Caterina Catanti, attended the ''istituto arcivescovile Santa Caterina'', and took part in the second war of Italian independence as ''sergente volontario''. He was a student of Carlo Matteucci and graduated in mathematics at Pisa under Riccardo Felici. He was appointed as assistant to the astronomer Giovanni Battista Donati in 1862, professor at the technological institute of Bologna in 1864, professor of physics at the University of Cagliari in 1873, and, finally, successor to his father in 1881 in the chair of technological physics at the University of Pisa. Among his students was Augusto Righi. Pacinotti died in Pisa. Scientific studies and invention of the dynamo He is best known for inventing an improved form of direct-current electrica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Permanent Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets. A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include the elements iron, nickel and cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weak ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hippolyte Pixii
Hippolyte Pixii (1808–1835) was an instrument maker from Paris, France. In 1832 he built an early form of alternating current electrical generator, based on the principle of electromagnetic induction discovered by Michael Faraday. Mohamed A. El-Sharkawi, ''Electric Energy: An Introduction, Third Edition'', CRC Press, 2015, ,page 3 Pixii's device was a spinning magnet, operated by a hand crank, where the north and south poles passed over a coil with an iron core. A current pulse was produced each time a pole passed over the coil. He also found that the current direction changed when the north pole passed over the coil after the south pole. Later, acting on a suggestion by André-Marie Ampère, other results were obtained by introducing a commutator which produced a pulsating direct current. At that time direct current was preferable to alternating current. Although Pixii did not fully understand electromagnetic induction, his device led to more sophisticated devices being constru ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 move a test charge between the two points. In the International System of Units, the derived unit for voltage is named '' volt''. 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 generator, inductors, and transformers). 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. A voltmeter can be used to measure the voltage between two points in a system. Often a common reference potential such as the ground of the system is used as one of the points. A voltage can represent either a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electric Current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving particles are called charge carriers, which may be one of several types of particles, depending on the conductor. In electric circuits the charge carriers are often electrons moving through a wire. In semiconductors they can be electrons or holes. In an electrolyte the charge carriers are ions, while in plasma, an ionized gas, they are ions and electrons. The SI unit of electric current is the ampere, or ''amp'', which is the flow of electric charge across a surface at the rate of one coulomb per second. The ampere (symbol: A) is an SI base unit. Electric current is measured using a device called an ammeter. Electric currents create magnetic fields, which are used in motors, generators, inductors, and transformers. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Commutator (electric)
A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine. Two or more electrical contacts called "brushes" made of a soft conductive material like carbon press against the commutator, making sliding contact with successive segments of the commutator as it rotates. The windings (coils of wire) on the armature are connected to the commutator segments. Commutators are used in direct current (DC) machines: dynamos (DC generators) and many DC motors as well as universal motors. In a motor the commutator applies electric current to the windings. By reversing the current direction in the rotating windings each half turn, a steady rotating force (torque) is produced. In a generator the commutator picks off the current generated in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets. A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include the elements iron, nickel and cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond wea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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