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Electricity Electricity Electricity is the set of physical phenomena associated with the presence and motion of electric charge. Although initially considered a phenomenon separate from magnetism, since the development of Maxwell's equations, both are recognized as part of a single phenomenon: electromagnetism. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others. The presence of an electric charge, which can be either positive or negative, produces an electric field. The movement of electric charges is an electric current and produces a magnetic field. When a charge is placed in a location with a nonzero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. Thus, if that charge were to move, the electric field would be doing work on the electric charge [...More...]  "Electricity" on: Wikipedia Yahoo 

Electric Potential An electric potential (also called the electric field potential, potential drop or the electrostatic potential) is the amount of work needed to move a unit positive charge from a reference point to a specific point inside the field without producing any acceleration. Typically, the reference point is Earth or a point at Infinity, although any point beyond the influence of the electric field charge can be used. According to classical electrostatics, electric potential is a scalar quantity denoted by V, equal to the electric potential energy of any charged particle at any location (measured in joules) divided by the charge of that particle (measured in coulombs). By dividing out the charge on the particle a quotient is obtained that is a property of the electric field itself. This value can be calculated in either a static (timeinvariant) or a dynamic (varying with time) electric field at a specific time in units of joules per coulomb (J C−1), or volts (V) [...More...]  "Electric Potential" on: Wikipedia Yahoo 

Electromagnetic Pulse An electromagnetic pulse (EMP), also sometimes called a transient electromagnetic disturbance, is a short burst of electromagnetic energy. Such a pulse's origination may be a natural occurrence or manmade and can occur as a radiated, electric, or magnetic field or a conducted electric current, depending on the source. EMP interference is generally disruptive or damaging to electronic equipment, and at higher energy levels a powerful EMP event such as a lightning strike can damage physical objects such as buildings and aircraft structures [...More...]  "Electromagnetic Pulse" on: Wikipedia Yahoo 

Eddy Current Eddy currents Eddy currents (also called Foucault currents) are loops of electrical current induced within conductors by a changing magnetic field in the conductor due to Faraday's law of induction. Eddy currents Eddy currents flow in closed loops within conductors, in planes perpendicular to the magnetic field. They can be induced within nearby stationary conductors by a timevarying magnetic field created by an AC electromagnet or transformer, for example, or by relative motion between a magnet and a nearby conductor. The magnitude of the current in a given loop is proportional to the strength of the magnetic field, the area of the loop, and the rate of change of flux, and inversely proportional to the resistivity of the material. By Lenz's law, an eddy current creates a magnetic field that opposes the change in the magnetic field that created it, and thus eddy currents react back on the source of the magnetic field [...More...]  "Eddy Current" on: Wikipedia Yahoo 

Lightning Lightning Lightning is a sudden electrostatic discharge that occurs typically during a thunderstorm. This discharge occurs between electrically charged regions of a cloud (called intracloud lightning or IC), between two clouds (CC lightning), or between a cloud and the ground (CG lightning). The charged regions in the atmosphere temporarily equalize themselves through this discharge referred to as a flash. A lightning flash can also be a strike if it involves an object on the ground [...More...]  "Lightning" on: Wikipedia Yahoo 

Insulator (electricity) An electrical insulator is a material whose internal electric charges do not flow freely; very little electric current will flow through it under the influence of an electric field. This contrasts with other materials, semiconductors and conductors, which conduct electric current more easily. The property that distinguishes an insulator is its resistivity; insulators have higher resistivity than semiconductors or conductors. A perfect insulator does not exist, because even insulators contain small numbers of mobile charges (charge carriers) which can carry current. In addition, all insulators become electrically conductive when a sufficiently large voltage is applied that the electric field tears electrons away from the atoms. This is known as the breakdown voltage of an insulator. Some materials such as glass, paper and Teflon, which have high resistivity, are very good electrical insulators [...More...]  "Insulator (electricity)" on: Wikipedia Yahoo 

Lenz's Law Lenz's law Lenz's law (pronounced /ˈlɛnts/), named after the physicist Heinrich Friedrich Emil Lenz who formulated it in 1834,[1] states that the direction of current induced in a conductor by a changing magnetic field due to induction is such that it creates a magnetic field that opposes the change that produced it. Lenz's law [...More...]  "Lenz's Law" on: Wikipedia Yahoo 

Poynting Vector In physics, the Poynting vector Poynting vector represents the directional energy flux (the energy transfer per unit area per unit time) of an electromagnetic field. The SI unit of the Poynting vector Poynting vector is the watt per square metre (W/m2) [...More...]  "Poynting Vector" on: Wikipedia Yahoo 

Liénard–Wiechert Potential Liénard–Wiechert potentials describe the classical electromagnetic effect of a moving electric point charge in terms of a vector potential and a scalar potential in the Lorenz gauge. Built directly from Maxwell's equations, these potentials describe the complete, relativistically correct, timevarying electromagnetic field for a point charge in arbitrary motion, but are not corrected for quantummechanical effects. Electromagnetic radiation Electromagnetic radiation in the form of waves can be obtained from these potentials [...More...]  "Liénard–Wiechert Potential" on: Wikipedia Yahoo 

Magnetization In classical electromagnetism, magnetization or magnetic polarization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. The origin of the magnetic moments responsible for magnetization can be either microscopic electric currents resulting from the motion of electrons in atoms, or the spin of the electrons or the nuclei. Net magnetization results from the response of a material to an external magnetic field, together with any unbalanced magnetic dipole moments that may be inherent in the material itself; for example, in ferromagnets. Magnetization Magnetization is not always uniform within a body, but rather varies between different points. Magnetization Magnetization also describes how a material responds to an applied magnetic field as well as the way the material changes the magnetic field, and can be used to calculate the forces that result from those interactions [...More...]  "Magnetization" on: Wikipedia Yahoo 

Maxwell Stress Tensor The Maxwell stress tensor Maxwell stress tensor (named after James Clerk Maxwell) is a symmetric secondorder tensor used in classical electromagnetism to represent the interaction between electromagnetic forces and mechanical momentum. In simple situations, such as a point charge moving freely in a homogeneous magnetic field, it is easy to calculate the forces on the charge from the Lorentz force Lorentz force law. When the situation becomes more complicated, this ordinary procedure can become impossibly difficult, with equations spanning multiple lines. It is therefore convenient to collect many of these terms in the Maxwell stress tensor, and to use tensor arithmetic to find the answer to the problem at hand. In the relativistic formulation of electromagnetism, the Maxwell's tensor appears as a part of the electromagnetic stress–energy tensor which is the electromagnetic component of the total stress–energy tensor [...More...]  "Maxwell Stress Tensor" on: Wikipedia Yahoo 

Electric Dipole Moment The electric dipole moment is a measure of the separation of positive and negative electrical charges within a system, that is, a measure of the system's overall polarity. The electricfield strength of the dipole is proportional to the magnitude of dipole moment. The SI units for electric dipole moment are coulombmeter (C·m); however, the most common unit is the debye (D). Theoretically, an electric dipole is defined by the firstorder term of the multipole expansion; it consists of two equal and opposite charges that are infinitely close together. This is unrealistic, as real dipoles have separated charge.[1] However, because the charge separation is very small compared to everyday lengths, the error introduced by treating real dipoles like they are theoretically perfect is usually negligible [...More...]  "Electric Dipole Moment" on: Wikipedia Yahoo 

London Equations The London equations, developed by brothers Fritz and Heinz London in 1935,[1] relate current to electromagnetic fields in and around a superconductor [...More...]  "London Equations" on: Wikipedia Yahoo 

Mathematical Descriptions Of The Electromagnetic Field There are various mathematical descriptions of the electromagnetic field that are used in the study of electromagnetism, one of the four fundamental interactions of nature [...More...]  "Mathematical Descriptions Of The Electromagnetic Field" on: Wikipedia Yahoo 

Magnetic Moment The magnetic moment of a magnet is a quantity that determines the torque it will experience in an external magnetic field. A loop of electric current, a bar magnet, an electron, a molecule, and a planet all have magnetic moments. The magnetic moment may be considered to be a vector having a magnitude and direction. The direction of the magnetic moment points from the south to north pole of the magnet (inside the magnet). The magnetic field produced by the magnet is proportional to its magnetic moment. More precisely, the term magnetic moment normally refers to a system's magnetic dipole moment, which produces the first term in the multipole expansion of a general magnetic field [...More...]  "Magnetic Moment" on: Wikipedia Yahoo 

Gauss's Law For Magnetism In physics, Gauss's law Gauss's law for magnetism is one of the four Maxwell's equations that underlie classical electrodynamics. It states that the magnetic field B has divergence equal to zero,[1] in other words, that it is a solenoidal vector field. It is equivalent to the statement that magnetic monopoles do not exist.[2] Rather than "magnetic charges", the basic entity for magnetism is the magnetic dipole. (If monopoles were ever found, the law would have to be modified, as elaborated below.) Gauss's law Gauss's law for magnetism can be written in two forms, a differential form and an integral form. These forms are equivalent due to the divergence theorem. The name " Gauss's law Gauss's law for magnetism"[1] is not universally used [...More...]  "Gauss's Law For Magnetism" on: Wikipedia Yahoo 