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History Of Electromagnetism The history of electromagnetic theory begins with ancient measures to understand atmospheric electricity, in particular lightning.[1] People then had little understanding of electricity, and were unable to explain the phenomena.[2] Scientific understanding into the nature of electricity grew throughout the eighteenth and nineteenth centuries through the work of researchers such as Ampère, Coulomb, Faraday and Maxwell. In the 19th century it had become clear that electricity and magnetism were related, and their theories were unified: wherever charges are in motion electric current results, and magnetism is due to electric current.[3] The source for electric field is electric charge, whereas that for magnetic field is electric current (charges in motion).Contents1 Ancient and classical history 2 Middle Ages and the Renaissance 3 18th century3.1 Improving the electric machine 3.2 Electrics and nonelectrics 3.3 Vitreous and resinous 3.4 Leyden jar 3.5 Late 18th cent [...More...]  "History Of Electromagnetism" on: Wikipedia Yahoo Parouse 

Ohm's Law Ohm's law Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance,[1] one arrives at the usual mathematical equation that describes this relationship:[2] I = V R , displaystyle I= frac V R , where I is the current through the conductor in units of amperes, V is the voltage measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law Ohm's law states that the R in this relation is constant, independent of the current.[3] The law was named after the German physicist Georg Ohm, who, in a treatise published in 1827, described measurements of applied voltage and current through simple electrical circuits containing various lengths of wire [...More...]  "Ohm's Law" on: Wikipedia Yahoo Parouse 

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 Parouse 

Lorentz Force In physics (particularly in electromagnetism) the Lorentz force Lorentz force is the combination of electric and magnetic force on a point charge due to electromagnetic fields. A particle of charge q moving with velocity v in the presence of an electric field E and a magnetic field B experiences a force F = q E + q v × B displaystyle mathbf F =qmathbf E +qmathbf v times mathbf B (in SI units[1][2]) [...More...]  "Lorentz Force" on: Wikipedia Yahoo Parouse 

Electromagnetic Induction Electromagnetic or magnetic induction is the production of an electromotive force (i.e., voltage) across an electrical conductor in a changing magnetic field. Michael Faraday Michael Faraday is generally credited with the discovery of induction in 1831, and James Clerk Maxwell James Clerk Maxwell mathematically described it as Faraday's law of induction. Lenz's law Lenz's law describes the direction of the induced field [...More...]  "Electromagnetic Induction" on: Wikipedia Yahoo Parouse 

Faraday's Law Of Induction Faraday's law of induction Faraday's law of induction is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF)—a phenomenon called electromagnetic induction. It is the fundamental operating principle of transformers, inductors, and many types of electrical motors, generators and solenoids.[1][2] The Maxwell–Faraday equation is a generalization of Faraday's law, and is listed as one of Maxwell's equations.Contents1 History 2 Faraday's law2.1 Qualitative statement 2.2 Quantitative 2.3 Maxwell–Faraday equation3 Proof of Faraday's law 4 EMF for nonthinwire circuits 5 Faraday's law and relativity5.1 Two phenomena 5.2 Einstein's view6 See also 7 References 8 Further reading 9 External linksHistory[edit]A diagram of Faraday's iron ring apparatus [...More...]  "Faraday's Law Of Induction" on: Wikipedia Yahoo Parouse 

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 Parouse 

Displacement Current In electromagnetism, displacement current density is the quantity ∂D/∂t appearing in Maxwell's equations Maxwell's equations that is defined in terms of the rate of change of D, the electric displacement field. Displacement current density has the same units as electric current density, and it is a source of the magnetic field just as actual current is. However it is not an electric current of moving charges, but a timevarying electric field. In physical materials (as opposed to vacuum), there is also a contribution from the slight motion of charges bound in atoms, called dielectric polarization. The idea was conceived by James Clerk Maxwell James Clerk Maxwell in his 1861 paper On Physical Lines of Force, Part III in connection with the displacement of electric particles in a dielectric medium. Maxwell added displacement current to the electric current term in Ampère's Circuital Law [...More...]  "Displacement Current" on: Wikipedia Yahoo Parouse 

Magnetic Potential The term magnetic potential can be used for either of two quantities in classical electromagnetism: the magnetic vector potential, A, (often simply called the vector potential) and the magnetic scalar potential, ψ. Both quantities can be used in certain circumstances to calculate the magnetic field. The more frequently used magnetic vector potential, A, is defined such that the curl of A is the magnetic field B. Together with the electric potential, the magnetic vector potential can be used to specify the electric field, E as well. Therefore, many equations of electromagnetism can be written either in terms of the E and B, or in terms of the magnetic vector potential and electric potential [...More...]  "Magnetic Potential" on: Wikipedia Yahoo Parouse 

Maxwell's Equations Maxwell's equations Maxwell's equations are a set of partial differential equations that, together with the Lorentz force Lorentz force law, form the foundation of classical electromagnetism, classical optics, and electric circuits. The equations provide a conceptual underpinning for all electric, optical and radio technologies, including power generation, electric motors, wireless communication, cameras, televisions, computers etc. Maxwell's equations describe how electric and magnetic fields are generated by charges, currents, and changes of each other. One important consequence of the equations is that they demonstrate how fluctuating electric and magnetic fields propagate at the speed of light. Known as electromagnetic radiation, these waves may occur at various wavelengths to produce a spectrum from radio waves to γrays [...More...]  "Maxwell's Equations" on: Wikipedia Yahoo Parouse 

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 Parouse 

Electromagnetic Radiation In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through spacetime, carrying electromagnetic radiant energy.[1] It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, Xrays, and gamma rays.[2] Classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light through a vacuum. The oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave. The wavefront of electromagnetic waves emitted from a point source (such as a light bulb) is a sphere. The position of an electromagnetic wave within the electromagnetic spectrum could be characterized by either its frequency of oscillation or its wavelength [...More...]  "Electromagnetic Radiation" on: Wikipedia Yahoo Parouse 

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 Parouse 

Electromagnetism Electromagnetism Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force usually exhibits electromagnetic fields such as electric fields, magnetic fields and light, and is one of the four fundamental interactions (commonly called forces) in nature. The other three fundamental interactions are the strong interaction, the weak interaction and gravitation.[1] Lightning Lightning is an electrostatic discharge that travels between two charged regions.The word electromagnetism is a compound form of two Greek terms, ἤλεκτρον ēlektron, "amber", and μαγνῆτις λίθος magnētis lithos,[2] which means "Μagnesian stone",[3] a type of iron ore [...More...]  "Electromagnetism" on: Wikipedia Yahoo Parouse 

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 Parouse 

Jefimenko's Equations In electromagnetism, Jefimenko's equations Jefimenko's equations (named after Oleg D. Jefimenko) give the electric field and magnetic field due to a distribution of electric charges and electric current in space, that takes into account the propagation delay (retarded time) of the fields due to the finite speed of light and relativistic effects. Therefore they can be used for moving charges and currents [...More...]  "Jefimenko's Equations" on: Wikipedia Yahoo Parouse 