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Faraday Cage
A Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields. A Faraday shield may be formed by a continuous covering of conductive material, or in the case of a Faraday cage, by a mesh of such materials. Faraday cages are named after scientist Michael Faraday, who invented them in 1836. A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed so that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment (for example RF receivers) from external radio frequency interference (RFI) often during testing or alignment of the device. They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes through the interior. Faraday cages ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cage De Faraday
A cage is an enclosure often made of mesh, bars, or wires, used to confine, contain or protect something or someone. A cage can serve many purposes, including keeping an animal or person in captivity, capturing an animal or person, and displaying an animal at a zoo. Construction Since a cage is usually intended to hold living beings, at least some part of its structure must be such as to allow for the entry of light and air. Thus some cages may be made with bars spaced too closely together for the intended captive to slip between them, or with windows covered by a mesh of some sort. Animal cages Cages are often used to confine animals, and some are specially designed to fit a certain species of animal. One or more birds, rodents, reptiles, and even larger animals of certain breeds are sometimes confined in a cage as pets. Animal cages have been a part of human culture since ancient times. For example, an Ancient Greek vase dated to 490 B.C. depicts a boy holding a possibly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wavelength
In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, troughs, or zero crossings, and is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter ''lambda'' (λ). The term ''wavelength'' is also sometimes applied to modulated waves, and to the sinusoidal envelopes of modulated waves or waves formed by interference of several sinusoids. Assuming a sinusoidal wave moving at a fixed wave speed, wavelength is inversely proportional to frequency of the wave: waves with higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. Wavelength depends on the medium (for example, vacuum, air, or water) that a wav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charge Carrier
In physics, a charge carrier is a particle or quasiparticle that is free to move, carrying an electric charge, especially the particles that carry electric charges in electrical conductors. Examples are electrons, ions and holes. The term is used most commonly in solid state physics. In a conducting medium, an electric field can exert force on these free particles, causing a net motion of the particles through the medium; this is what constitutes an electric current. In conducting media, particles serve to carry charge: *In many metals, the charge carriers are electrons. One or two of the valence electrons from each atom are able to move about freely within the crystal structure of the metal. The free electrons are referred to as conduction electrons, and the cloud of free electrons is called a Fermi gas. Many metals have electron and hole bands. In some, the majority carriers are holes. *In electrolytes, such as salt water, the charge carriers are ions, which are atoms or molecul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Faraday Cage
A Faraday cage or Faraday shield is an enclosure used to block electromagnetic fields. A Faraday shield may be formed by a continuous covering of conductive material, or in the case of a Faraday cage, by a mesh of such materials. Faraday cages are named after scientist Michael Faraday, who invented them in 1836. A Faraday cage operates because an external electrical field causes the electric charges within the cage's conducting material to be distributed so that they cancel the field's effect in the cage's interior. This phenomenon is used to protect sensitive electronic equipment (for example RF receivers) from external radio frequency interference (RFI) often during testing or alignment of the device. They are also used to protect people and equipment against actual electric currents such as lightning strikes and electrostatic discharges, since the enclosing cage conducts current around the outside of the enclosed space and none passes through the interior. Faraday cages ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abbe Nollet
Jean-Antoine Nollet (; 19 November 170025 April 1770) was a French clergyman and physicist who did a number of experiments with electricity and discovered osmosis. As a deacon in the Catholic Church, he was also known as Abbé Nollet. Biography Nollet studied humanities at the Collège de Clermont in Beauvais, starting in 1715. He completed a master's degree in the Faculty of Theology at the University of Paris in 1724. He was ordained a deacon in the Catholic Church in 1728, but suspended his clerical career. However he used the title of Abbé throughout his life. Nollet was particularly interested in the new science of electricity. He joined the Société des Arts in 1728, an association which was reestablished from a previous version which ended in 1723. Formed under the patronage of Comte de Clermont, the Société focused on applying natural philosophy to practical arts. This association gave Nollet the opportunity to come into contact with important natural philosophers. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benjamin Franklin
Benjamin Franklin ( April 17, 1790) was an American polymath who was active as a writer, scientist, inventor, statesman, diplomat, printer, publisher, and political philosopher. Encyclopædia Britannica, Wood, 2021 Among the leading intellectuals of his time, Franklin was one of the Founding Fathers of the United States, a drafter and signer of the United States Declaration of Independence, and the first United States Postmaster General. As a scientist, he was a major figure in the American Enlightenment and the history of physics for his studies of electricity, and for charting and naming the current still known as the Gulf Stream. As an inventor, he is known for the lightning rod, bifocals, and the Franklin stove, among others. He founded many civic organizations, including the Library Company, Philadelphia's first fire department, and the University of Pennsylvania. Isaacson, 2004, p. Franklin earned the title of "The First American" for his early and indefa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Faraday's Ice Pail Experiment
Faraday's ice pail experiment is a simple electrostatics experiment performed in 1843 by British scientist Michael Faraday that demonstrates the effect of electrostatic induction on a conducting container. For a container, Faraday used a metal pail made to hold ice, which gave the experiment its name.John Ambrose Fleming, The experiment shows that an electric charge enclosed inside a conducting shell induces an equal charge on the shell, and that in an electrically conducting body, the charge resides entirely on the surface. It also demonstrates the principles behind electromagnetic shielding such as employed in the ''Faraday cage''. The ice pail experiment was the first precise ''quantitative'' experiment on electrostatic charge. It is still used today in lecture demonstrations and physics laboratory courses to teach the principles of electrostatics. Description of experiment Faraday's description of the experiment, from a letter he wrote on February 4, 1843 to Richard Phill ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electroscope
The electroscope is an early scientific instrument used to detect the presence of electric charge on a body. It detects charge by the movement of a test object due to the Coulomb electrostatic force on it. The amount of charge on an object is proportional to its voltage. The accumulation of enough charge to detect with an electroscope requires hundreds or thousands of volts, so electroscopes are used with high voltage sources such as static electricity and electrostatic machines. An electroscope can only give a rough indication of the quantity of charge; an instrument that measures electric charge quantitatively is called an electrometer. The electroscope was the first electrical measuring instrument. The first electroscope was a pivoted needle (called the ''versorium''), invented by British physician William Gilbert around 1600. a translation by P. Fleury Mottelay of William Gilbert (1600) ''Die Magnete'', London The pith-ball electroscope and the gold-leaf electroscope ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio-frequency Identification
Radio-frequency identification (RFID) uses electromagnetic fields to automatically identify and track tags attached to objects. An RFID system consists of a tiny radio transponder, a radio receiver and transmitter. When triggered by an electromagnetic interrogation pulse from a nearby RFID reader device, the tag transmits digital data, usually an identifying inventory number, back to the reader. This number can be used to track inventory goods. Passive tags are powered by energy from the RFID reader's interrogating radio waves. Active tags are powered by a battery and thus can be read at a greater range from the RFID reader, up to hundreds of meters. Unlike a barcode, the tag does not need to be within the line of sight of the reader, so it may be embedded in the tracked object. RFID is one method of automatic identification and data capture (AIDC). RFID tags are used in many industries. For example, an RFID tag attached to an automobile during production can be used to track ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antenna (radio)
In radio engineering, an antenna or aerial is the interface between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. In transmission, a radio transmitter supplies an electric current to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic wave In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visib ...s (radio waves). In Receiver (radio), reception, an antenna intercepts some of the power of a radio wave in order to produce an electric current at its terminals, that is applied to a receiver to be Amplifier, amplified. Antennas are essential components of all radio equipment. An antenna is an array of conductor (material), conductors (Driven element, elements), elect ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Waves
Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (shorter than a grain of rice); at 30 Hz the corresponding wavelength is (longer than the radius of the Earth). Like all electromagnetic waves, radio waves in a vacuum travel at the speed of light, and in the Earth's atmosphere at a close, but slightly lower speed. Radio waves are generated by charged particles undergoing acceleration, such as time-varying electric currents. Naturally occurring radio waves are emitted by lightning and astronomical objects, and are part of the blackbody radiation emitted by all warm objects. Radio waves are generated artificially by an electronic device called a transmitter, which is connected to an antenna which radiates the waves. They are received by another antenna connected to a radio receiver, which p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electromagnetic Pulse
An electromagnetic pulse (EMP), also a transient electromagnetic disturbance (TED), is a brief burst of electromagnetic energy. Depending upon the source, the origin of an EMP can be natural or artificial, and can occur as an electromagnetic field, as an electric field, as a magnetic field, or as a conducted electric current. The electromagnetic interference caused by an EMP disrupts communications and damages electronic equipment; at higher levels of energy, an EMP such as a lightning strike can physically damage objects such as buildings and aircraft. The management of EMP effects is a branch of electromagnetic compatibility (EMC) engineering. EMP weapons are designed to deliver the damaging effects of a high-energy EMP that will disrupt unprotected infrastructure in the country, thus the employment of an EMP weapon against a country is the scenario of war most likely to collapse the functionality of the electrical network of the country. General characteristics An electrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
