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Electromagnetic Wave
In physics , ELECTROMAGNETIC RADIATION (EM RADIATION or EMR) refers to the waves (or their quanta, photons ) of the electromagnetic field , propagating (radiating) through space carrying electromagnetic radiant energy . It includes radio waves , microwaves , infrared , (visible) light , ultraviolet , X- , and gamma radiation. 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 lightbulb) 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 . The electromagnetic spectrum includes, in order of increasing frequency and decreasing wavelength: radio waves, microwaves, infrared radiation, visible light , ultraviolet radiation, X-rays and gamma rays . Electromagnetic waves are produced whenever charged particles are accelerated , and these waves can subsequently interact with other charged particles. EM waves carry energy , momentum and angular momentum away from their source particle and can impart those quantities to matter with which they interact
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Transverse Wave
A TRANSVERSE WAVE is a moving wave that consists of oscillations occurring perpendicular (right angled) to the direction of energy transfer (or the propagation of the wave). If a transverse wave is moving in the positive x-direction, its oscillations are in up and down directions that lie in the y–z plane. Light is an example of a transverse wave, while sound is a longitudinal wave . A ripple in a pond and a wave on a string are easily visualized as transverse waves. CONTENTS* 1 Explanation * 1.1 "Polarized" waves * 1.2 Electromagnetic waves * 2 See also * 3 References * 4 External links EXPLANATIONTransverse waves are waves that are oscillating perpendicularly to the direction of propagation. If you anchor one end of a ribbon or string and hold the other end in your hand, you can create transverse waves by moving your hand up and down. Notice though, that you can also launch waves by moving your hand side-to-side. This is an important point. There are two independent directions in which wave motion can occur. In this case, these motions are the y and z directions mentioned above, while the wave propagates away in the x direction. "POLARIZED" WAVESSee the full article concerning Polarization (waves) Continuing with the string example, if you move your hand in a clockwise circle, you will launch waves in the form of a left-handed helix as they propagate away
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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 . 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_, which means "Μagnesian stone", a type of iron ore . Electromagnetic phenomena are defined in terms of the electromagnetic force, sometimes called the Lorentz force , which includes both electricity and magnetism as different manifestations of the same phenomenon . The electromagnetic force plays a major role in determining the internal properties of most objects encountered in daily life. Ordinary matter takes its form as a result of intermolecular forces between individual atoms and molecules in matter, and is a manifestation of the electromagnetic force
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Electricity
ELECTRICITY is the set of physical phenomena associated with the presence 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. In addition, electricity is at the heart of many modern technologies. The presence of an electric charge, which can be either positive or negative, produces an electric field . On the other hand, the movement of electric charges, which is known as electric current , produces a magnetic field . When a charge is placed in a location with non-zero 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. Thus we can speak of electric potential at a certain point in space, which is equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is typically measured in volts
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Magnetism
MAGNETISM is a class of physical phenomena that are mediated by magnetic fields . Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets , producing magnetic fields themselves. Only a few substances are ferromagnetic; the most common ones are iron , nickel and cobalt and their alloys. The prefix _ferro-_ refers to iron , because permanent magnetism was first observed in lodestone , a form of natural iron ore called magnetite , Fe3O4. Although ferromagnetism is responsible for most of the effects of magnetism encountered in everyday life, all other materials are influenced to some extent by a magnetic field, by several other types of magnetism. Paramagnetic substances such as aluminum and oxygen are weakly attracted to an applied magnetic field; diamagnetic substances such as copper and carbon are weakly repelled; while antiferromagnetic materials such as chromium and spin glasses have a more complex relationship with a magnetic field. The force of a magnet on paramagnetic, diamagnetic, antiferromagnetic materials is usually too weak to be felt, and can be detected only by laboratory instruments, so in everyday life these substances are often described as non-magnetic
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Electrostatics
ELECTROSTATICS is a branch of physics that deals with study of the electric charges at rest. Since classical physics , it has been known that some materials such as amber attract lightweight particles after rubbing . The Greek word for amber, ήλεκτρον, or _electron_, was the source of the word 'electricity'. Electrostatic phenomena arise from the forces that electric charges exert on each other. Such forces are described by Coulomb\'s law . Even though electrostatically induced forces seem to be rather weak, some electrostatic forces such as the one between an electron and a proton , that together make up a hydrogen atom , is about 36 orders of magnitude stronger than the gravitational force acting between them. There are many examples of electrostatic phenomena, from those as simple as the attraction of the plastic wrap to your hand after you remove it from a package to the apparently spontaneous explosion of grain silos, the damage of electronic components during manufacturing, and photocopier "> q {displaystyle q} and Q {displaystyle Q} (in coulombs ). It is convenient to label one of these charges, q {displaystyle q} , as a test charge , and call Q {displaystyle Q} a source charge. As we develop the theory, more source charges will be added
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Electric Charge
ELECTRIC CHARGE is the physical property of matter that causes it to experience a force when placed in an electromagnetic field . There are two types of electric charges: positive and negative (commonly carried by protons and electrons respectively). Like charges repel and unlike attract. An absence of net charge is referred to as neutral. An object is negatively charged if it has an excess of electrons , and is otherwise positively charged or uncharged. The SI derived unit of electric charge is the coulomb (C). In electrical engineering , it is also common to use the ampere-hour (Ah), and, in chemistry , it is common to use the elementary charge (e) as a unit. The symbol Q often denotes charge. Early knowledge of how charged substances interact is now called classical electrodynamics , and is still accurate for problems that don't require consideration of quantum effects . The electric charge is a fundamental conserved property of some subatomic particles , which determines their electromagnetic interaction . Electrically charged matter is influenced by, and produces, electromagnetic fields . The interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force , which is one of the four fundamental forces (See also: magnetic field )
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Static Electricity
STATIC ELECTRICITY is an imbalance of electric charges within or on the surface of a material. The charge remains until it is able to move away by means of an electric current or electrical discharge . Static electricity is named in contrast with current electricity , which flows through wires or other conductors and transmits energy . A static electric charge can be created whenever two surfaces contact and separate, and at least one of the surfaces has a high resistance to electric current (and is therefore an electrical insulator ). The effects of static electricity are familiar to most people because people can feel, hear, and even see the spark as the excess charge is neutralized when brought close to a large electrical conductor (for example, a path to ground), or a region with an excess charge of the opposite polarity (positive or negative). The familiar phenomenon of a static shock–more specifically, an electrostatic discharge –is caused by the neutralization of charge
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Electric Field
An ELECTRIC FIELD is a vector field that associates to each point in space the Coulomb force that would be experienced per unit of electric charge , by an infinitesimal test charge at that point. Electric fields are created by electric charges and can be induced by time-varying magnetic fields . The electric field combines with the magnetic field to form the electromagnetic field . CONTENTS * 1 Definition * 2 Sources of electric field * 2.1 Causes and description * 2.2 Continuous vs. discrete charge representation * 3 Superposition principle * 4 Electrostatic fields * 4.1 Electric potential * 4.2 Parallels between electrostatic and gravitational fields * 4.3 Uniform fields * 5 Electrodynamic fields * 6 Energy in the electric field * 7 Further extensions * 7.1 Definitive equation of vector fields * 7.2 Constitutive relation * 8 See also * 9 References * 10 External links DEFINITIONThe electric field, E {displaystyle mathbf {E} } , at a given point is defined as the (vector) force, F {displaystyle mathbf {F} } , that would be exerted on a stationary test particle of unit charge by electromagnetic forces (i.e. the Lorentz force ). A particle of charge q {displaystyle q} would be subject to a force F = q E {displaystyle mathbf {F} =qmathbf {E} }
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Electrical Conductor
In physics and electrical engineering , a CONDUCTOR is an object or type of material that allows the flow of an electrical current in one or more directions. Materials made of metal are common electrical conductors. Electrical current is generated by the flow of negatively charged electrons, positively charged holes, and positive or negative ions in some cases. In order for current to flow, it is not necessary for one charged particle to travel from the machine producing the current to that consuming it. Instead, the charged particle simply needs to nudge its neighbor a finite amount who will nudge its neighbor and on and on until a particle is nudged into the consumer, thus powering the machine. Essentially what is occurring here is a long chain of momentum transfer between mobile charge carriers; the Drude model of conduction describes this process more rigorously. This momentum transfer model makes metal an ideal choice for a conductor as metals, characteristically, possess a delocalized sea of electrons which gives the electrons enough mobility to collide and thus effect a momentum transfer. As discussed above, electrons are the primary mover in metals; however, other devices such as the cationic electrolyte (s) of a battery , or the mobile protons of the proton conductor of a fuel cell rely on positive charge carriers. Insulators are non-conducting materials with few mobile charges that support only insignificant electric currents
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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. A much larger class of materials, even though they may have lower bulk resistivity, are still good enough to prevent significant current from flowing at normally used voltages, and thus are employed as insulation for electrical wiring and cables . Examples include rubber-like polymers and most plastics which can be thermoset or thermoplastic in nature. Insulators are used in electrical equipment to support and separate electrical conductors without allowing current through themselves
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Triboelectric Effect
The TRIBOELECTRIC EFFECT (also known as TRIBOELECTRIC CHARGING) is a type of contact electrification in which certain materials become electrically charged after they come into frictional contact with a different material. Rubbing glass with fur, or a plastic comb through the hair, can build up triboelectricity. Most everyday static electricity is triboelectric. The polarity and strength of the charges produced differ according to the materials, surface roughness, temperature, strain, and other properties. The triboelectric effect is not very predictable, and only broad generalizations can be made. Amber , for example, can acquire an electric charge by contact and separation (or friction ) with a material like wool . This property was first recorded by Thales of Miletus . The word "electricity " is derived from William Gilbert 's initial coinage, "electra", which originates in the Greek word for amber, ēlektron. The prefix tribo- (Greek for ‘rub’) refers to ‘friction’, as in tribology . Other examples of materials that can acquire a significant charge when rubbed together include glass rubbed with silk , and hard rubber rubbed with fur . The triboelectric effect is now considered to be related to the phenomenon of adhesion , where two materials composed of different molecules tend to stick together because of attraction between the different molecules
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Electrostatic Discharge
ELECTROSTATIC DISCHARGE (ESD) is the sudden flow of electricity between two electrically charged objects caused by contact, an electrical short , or dielectric breakdown . A buildup of static electricity can be caused by tribocharging or by electrostatic induction . The ESD occurs when differently-charged objects are brought close together or when the dielectric between them breaks down, often creating a visible spark . ESD can create spectacular electric sparks (lightning , with the accompanying sound of thunder , is a large-scale ESD event), but also less dramatic forms which may be neither seen nor heard, yet still be large enough to cause damage to sensitive electronic devices. Electric sparks require a field strength above approximately 40 kV/cm in air, as notably occurs in lightning strikes. Other forms of ESD include corona discharge from sharp electrodes and brush discharge from blunt electrodes. ESD can cause a range of harmful effects of importance in industry, including gas, fuel vapour and coal dust explosions, as well as failure of solid state electronics components such as integrated circuits . These can suffer permanent damage when subjected to high voltages. Electronics manufacturers therefore establish electrostatic protective areas free of static, using measures to prevent charging, such as avoiding highly charging materials and measures to remove static such as grounding human workers, providing antistatic devices , and controlling humidity
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Electrostatic Induction
ELECTROSTATIC INDUCTION, also known as "electrostatic influence" or simply "influence" in Europe and Latin America, is a redistribution of electrical charge in an object, caused by the influence of nearby charges. In the presence of a charged body, an insulated conductor develops a positive charge on one end and a negative charge on the other end. Induction was discovered by British scientist John Canton in 1753 and Swedish professor Johan Carl Wilcke in 1762. Electrostatic generators , such as the Wimshurst machine , the Van de Graaff generator and the electrophorus , use this principle. Due to induction, the electrostatic potential (voltage ) is constant at any point throughout a conductor. Electrostatic Induction is also responsible for the attraction of light nonconductive objects, such as balloons, paper or styrofoam scraps, to static electric charges. Electrostatic induction laws apply in dynamic situations as far as the quasistatic approximation is valid. Electrostatic induction should not be confused with Electromagnetic induction . CONTENTS * 1 Explanation * 2 Charging an object by induction * 3 The electrostatic field inside a conductive object is zero * 4 Induced charge resides on the surface * 5 The voltage throughout a conductive object is constant * 6 Induction in dielectric objects * 7 Notes * 8 External links EXPLANATION Play media Using an electroscope to show electrostatic induction
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Coulomb's Law
COULOMB\'S LAW, or COULOMB\'S inverse-square law , is a law of physics that describes force interacting between static electrically charged particles. In its scalar form, the law is: F = k e q 1 q 2 r 2 {displaystyle F=k_{e}{frac {q_{1}q_{2}}{r^{2}}}} , where ke is Coulomb\'s constant (ke = 7009899000000000000♠8.99×109 N m2 C−2), q1 and q2 are the signed magnitudes of the charges, and the scalar r is the distance between the charges. The force of interaction between the charges is attractive if the charges have opposite signs (i.e., F is negative) and repulsive if like-signed (i.e., F is positive). The law was first published in 1784 by French physicist Charles Augustin de Coulomb and was essential to the development of the theory of electromagnetism . It is analogous to Isaac Newton 's inverse-square law of universal gravitation . Coulomb's law can be used to derive Gauss\'s law , and vice versa. The law has been tested extensively , and all observations have upheld the law's principle
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Gauss' Law
In physics , GAUSS\' LAW, also known as GAUSS\' FLUX THEOREM, is a law relating the distribution of electric charge to the resulting electric field . The law was first formulated by Joseph-Louis Lagrange in 1773, followed by Carl Friedrich Gauss in 1813, both in the context of the attraction of ellipsoids. It is one of Maxwell\'s four equations , which form the basis of classical electrodynamics . Gauss' law can be used to derive Coulomb\'s law , and vice versa. CONTENTS * 1 Qualitative description * 2 Equation involving the E field * 2.1 Integral form * 2.1.1 Applying the integral form * 2.2 Differential form * 2.3 Equivalence of integral and differential forms * 3 Equation involving the D field * 3.1 Free, bound, and total charge * 3.2 Integral form * 3.3 Differential form * 4 Equivalence of total and free charge statements * 5 Equation for linear materials * 6 Interpretations * 6.1 In terms of fields of force * 7 Relation to Coulomb\'s law * 7.1 Deriving Gauss\' law from Coulomb\'s law * 7.2 Deriving Coulomb\'s law from Gauss\' law * 8 See also * 9 Notes * 10 Citations * 11 References * 12 External links QUALITATIVE DESCRIPTIONIn words, Gauss' law states that: The net electric flux through any hypothetical closed surface is equal to 1/ε times the net electric charge within that closed surface
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