Can anyone explain Maxwell's (Four) Equations of Electro-Magnetism, in a simple, physical manner? I'm confused
818946
OK, here they are verbally:\n\n"Maxwell's four equations express, respectively, how electric charges produce electric fields (Gauss' law), the experimental absence of magnetic monopoles, how currents and changing electric fields produce magnetic fields (the Ampere-Maxwell law), and how changing magnetic fields produce electric fields (Faraday's law of induction)." [See source.]\n\nGauss' Law--simply says electrons in motion will create a force field around the current.  This law follows the inverse square of the distance rule and the phenomenon is the basis for radio and TV broadcasting waves.\n\nThe monopole equation simply says that there must be both a north and south pole in magnetism.  (However, sometimes fictitious monopoles are used mathematically to solve some problems.)\n\nThe Ampere-Maxwell equation links changing electrical current to the creation of magnetic flux.  The Faraday equation links changing magnetic flux to the creation of electrical current.  This is the stuff that electric motors and electric generators are made of.\n\nThe Maxwell equations have a lot of practical applications.  Wave guides, such as for high powered radars, and coax cables, like for your TV, are designed using Maxwall equations.
81056
ja :), that's a good one. E=mc^2 talks about the equivalence between matter and energy; c is just the constant that joins them both ..you won't attain a c ¨velocity¨out of it ; you'll just have to use \n E=mc^2/(sqrt(1-(v/c)^2) ( Is it Lorenz transf?) and I think Xav was pretty clear with his explanation! :)
233968
Biot-Savart law for a generalized current j can be written as:\n\n1) B(r) = μ0/4π rot ∫d³r' j(r')/|r - r'|\n\n\nthe scaled integral is a vector field, called the magnetic potential A:\n\nA(r) := μ0/4π ∫d³r' j(r')/|r - r'|\n\n\ntherewith you can write (1) as:\n\n2) B = rot A\n\n\nA is not unique. you can choose any scalar χ:\n\nA := A' + grad χ\n\nto satisfy equation (2), because for any χ\n\nrot grad χ == 0\n\n\nCoulomb Gauge: choose χ so that div A == 0\n\n\n\nMaxwell equations of Magnetostatics:\n\nM1) rot B == μ0 j\nM2) div B == 0\n\n\nequation (M1) with (2):\n\n<=> μ0 j == rot rot A\n\n<=> μ0 j == grad div A - ∆A \n\nwith Coulomb Gauge div A == 0\n\n<=> ∆A = - μ0 j\n\n\nThis equation is the fundamental problem of Magnetostatics:\n\n\ni ) given the current j in the volume V with the boundary condition ∂(V),\n\nii) solve ∆A == - μ0 j\n\n\nattend to the analogy to Electrostatics.\n\nPoisson Equation: ∆φ = - 1/ε0 ρ(r)\n\n\nThe problem is that the magnetic vector potential A is more abstract than its electrostatic scalar counterpart φ.
335873
In electromagnetic theory, the continuity equation is derived from two of Maxwell's equations. It states that the divergence of the current density is equal to the negative rate of change of the charge density,\n\n    &#92;nabla &#92;cdot &#92;mathbf{J} = - {&#92;partial &#92;rho &#92;over &#92;partial t}\n\n[edit]\n\nDerivation\n\nOne of Maxwell's equations states that\n\n    &#92;nabla &#92;times &#92;mathbf{H} = &#92;mathbf{J} + {&#92;partial &#92;mathbf{D} &#92;over &#92;partial t}.\n\nTaking the divergence of both sides results in\n\n    &#92;nabla &#92;cdot &#92;nabla &#92;times &#92;mathbf{H} = &#92;nabla &#92;cdot &#92;mathbf{J} + {&#92;partial &#92;nabla &#92;cdot &#92;mathbf{D} &#92;over &#92;partial t},\n\nbut the divergence of a curl is zero, so that\n\n    &#92;nabla &#92;cdot &#92;mathbf{J} + {&#92;partial &#92;nabla &#92;cdot &#92;mathbf{D} &#92;over &#92;partial t} = 0. &#92;qquad &#92;qquad (1)\n\nAnother one of Maxwell's equations states that\n\n    &#92;nabla &#92;cdot &#92;mathbf{D} = &#92;rho.&#92;,\n\nSubstitute this into equation (1) to obtain\n\n    &#92;nabla &#92;cdot &#92;mathbf{J} + {&#92;partial &#92;rho &#92;over &#92;partial t} = 0,&#92;,\n\nwhich is the continuity equation.\n[edit]\n\nInterpretation\n\nCurrent density is the movement of charge density. The continuity equation says that if charge is moving out of a differential volume (i.e. divergence of current density is positive) then the amount of charge within that volume is going to decrease, so the rate of change of charge density is negative. Therefore the continuity equation amounts to a conservation of charge.\n[edit]\n\nFluid dynamics\n\nIn fluid dynamics, a continuity equation is an equation of conservation of mass. Its differential form is\n\n    {&#92;partial &#92;rho &#92;over &#92;partial t} + &#92;nabla &#92;cdot (&#92;rho &#92;mathbf{u}) = 0\n\nwhere ρ is density, t is time, and u is fluid velocity.\n[edit]\n\nQuantum mechanics\n\nIn quantum mechanics, the conservation of probability also yields a continuity equation. Let P(x, t) be a probability density and write\n\n    &#92;nabla &#92;cdot &#92;mathbf{j} = -{ &#92;partial &#92;over &#92;partial t} P(x,t)\n\nwhere J is probability flux.
695383
true... this is a written law.. the faraday's law..in electromagnetics..
598602
Since Magnetic field (B) = [K I(dl x r)]/r^3\n\nwhere I = current in the conductor\n      r = distance of the pt. from the conductor where u  want to find the magnetic field\n\nHere dl x r = vector product of small part of L i.e dl and r\n\nSee here that Magnetic field is directly proportional to Current....therefore when we increase the current by a factor of 4, magnetic field will also increase by a factor of 4.
585103
a positive and negitive charge attact eachother because of the electromagnetic force, which suggests that 2 charged particles will exert a force on eachother.\n\nTo find the magnetitude and direction of the force you use Coulombs law:\n\nF = (1/4πε).(q1q2/|r|²).r
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Magnetic flux and electric flux are always linked with each other.\n\nIf a magnetic flux changes in a certain region in space, a rotational electric field is produced.\n\nA varying magnetic field is inseparable from an electric field.\n\nThe division of electric fields into electric and magnetic fields is a relative matter.\n\nFrom one point there is only a magnetic field in space. From another view point in addition to the magnetic field there is an electric field. \n\nThe converse is also true.\n\nIf an observer in one system of coordinates finds only an electrical field present, then an observer in another inertial system will find that both an electrical field and magnetic field exist.
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Faraday's law of Electromagnetic induction: refer http://en.wikipedia.org/wiki/Electromagnetic_induction\n\nThermodynamic processes: refer http://en.wikipedia.org/wiki/Thermodynamics
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http://en.wikipedia.org/wiki/Magnets\n\ngo there if u wanna find out, i only know simple version...
1153313
gravity, strong force, weak force, and electromagnetivity
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The electric field and the magnetic field are perpendicular to each other.  They are also both perpendicular to the direction in which the wave is traveling.  So picture it like this:  If the electromagnetic wave is going East, then the magnetic field would be going South/North, and the Electric Field would be going Up/Down.  \n\nThat's a very simplified illustration, but it's the basic concept.
603730
The following refers to Coulomb force between two charges in a single uniform medium, not the two-medium situation described in  the question.\nAnswer 1 is helpful but the lack of exponent signs makes it misleading. The force is inversely proportional to the square of the distance, so the simplified formula is \nF = k * q1 * q2 / r^2 \nk is a constant = 8.99*10^9 N m^2 / C^2 (C is charge in Coulombs). Thus if q1 = q2 = 1 Coulomb, and q1 is separated from q2 by r = 1 meter, the force is 8.99*10^9 N or 2.01 billion pounds! \nThe above simplified formula is a contraction of the full formula (see ref.),\nF = q1 * q2 / (4 * pi * epsilon * r^2)\nin which k is replaced by 1/(4 * pi * epsilon), where epsilon is the product of epsilon0, the electrical permittivity of the vacuum (= 8.85 * 10^-12 c^2/(N m^2)), and kappa, the dielectric constant which = 1 for vacuum and is assumed in the simplified formula.\nFor two segments of distance as you specify, first solve for F1 and F2, each as a function of a particular distance (r or d - r) and dielectric constant. Then my inclination would be to try the sum-of-inverse square root solution which works for a similar situation, gravitational force F at distance R, computed from F1 and F2 at partial distances R1 and R2, where R = R1 + R2, \n1/SQRT(F) = 1/SQRT(F1) + 1/SQRT(F2)\nSorry I can't be more definite than that.
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Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, which exerts a force on those particles that possess the property of electric charge, and is in turn affected by the presence and motion of such particles. The term electrodynamics is sometimes used to refer to the combination of electromagnetism with mechanics, and deals with the effects of the electromagnetic field on the dynamic behavior of electrically charged particles. Electromagnetism encompasses various real-world electromagnetic phenomena.\n\n\nIt is often convenient to understand the electromagnetic field in terms of two separate fields: the electric field and the magnetic field. A non-zero electric field is produced by the presence of electrically charged particles, and gives rise to the electric force; this is the force that causes static electricity and drives the flow of electric charge (electric current) in electrical conductors. The magnetic field, on the other hand, can be produced by the motion of electric charges, or electric current, and gives rise to the magnetic force associated with magnets.\n\nThe term "electromagnetism" comes from the fact that the electric and magnetic fields generally cannot be described independently of one another. A changing magnetic field produces an electric field (this is the phenomenon of electromagnetic induction, which underlies the operation of electrical generators, induction motors, and transformers). Similarly, a changing electric field generates a magnetic field.\n\nBecause of this interdependence of the electric and magnetic fields, it makes sense to consider them as a single, theoretically coherent entity — the electromagnetic field. This unification, which was completed by James Clerk Maxwell, is one of the triumphs of 19th century physics. It had far-reaching consequences, one of which was the elucidation of the nature of light: as it turns out, what we think of as "light" is actually a propagating oscillatory disturbance in the electromagnetic field, i.e., an electromagnetic wave. Different frequencies of oscillation give rise to the different forms of electromagnetic radiation, from radio waves at the lowest frequencies, to visible light at intermediate frequencies, to gamma rays at the highest frequencies.\n\nThe theoretical implications of electromagnetism led to the development of special relativity by Albert Einstein in 1905.\n\nedit SI electromagnetism units \nSymbol Name of Quantity Derived Units  Base Units \nI Current ampere (SI base unit) A A \nq Electric charge, Quantity of electricity coulomb C A·s \nV Potential difference volt V J/C = kg·m2·s−3·A−1 \nR, Z Resistance, Impedance, Reactance ohm Ω V/A = kg·m2·s−3·A−2 \nρ Resistivity ohm metre Ω·m kg·m3·s−3·A−2 \nP Power, Electrical watt W V·A = kg·m2·s−3 \nC Capacitance farad F C/V = kg−1·m−2·A2·s4 \n Elastance reciprocal farad F−1 V/C = kg·m2·A−2·s−4 \nε Permittivity farad per metre F/m kg−1·m−3·A2·s4 \nχe Electric susceptibility (dimensionless) - - \n Conductance, Admittance, Susceptance siemens S Ω−1 = kg−1·m−2·s3·A2 \nσ Conductivity siemens per metre S/m kg−1·m−3·s3·A2 \nH Magnetic field, magnetic field intensity ampere per metre A/m A·m−1 \nΦm Magnetic flux weber Wb V·s = kg·m2·s−2·A−1 \nB Magnetic flux density, magnetic induction, magnetic field strength tesla T Wb/m2 = kg·s−2·A−1 \n Reluctance ampere-turns per weber A/Wb kg−1·m−2·s2·A2 \nL Inductance henry H Wb/A = V·s/A = kg·m2·s−2·A−2 \nμ Permeability henry per metre H/m kg·m·s−2·A−2 \nχm Magnetic susceptibility (dimensionless) - -
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a)It is already a magnet. It can not become an electromagnet.\nb)Can not happen\nc)If this happens it will only be for a short period\nd)After a long time its power may be reduced but not lost completely\n\nSo I can not tell for sure. Mots likely c
933992
the law states that if a wire with length L carries a current i, then a magnetic field is induced...  the magnetic field b (at a point r away) should be induced.... \n\nthe vector notations like dL (hat) and r (hat) are important because the direction of your induced magnetic field is determined using vecor algebra.... you can use the right thumb rule for that too.... the direction of the induced magnetic field  depends on the direction of your current that pass through the wire...\n\nnotice the magnetic field (look at the formula) is a vector quantity since length vector is crossed to the displacement vector....\n(vector cross vector is vector\nand vector dot vector is scalar)
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1) Magnetic field due to a current passing in a circular loop:\n        B=(PIN)/2r where\n  P is the permeability of the medium\n  I is the electric current\n  N is the number of turns\n  r is the radius of the loop\n\n2) Magnetic field due to a current in a soleniod:\n         B=(PIN)/L\n         B=PIn     where\n   P is the permeability of the medium\n   I is the electric current\n   N is the number of turns\n   L is the length of the coil\n   n is the number of turns per unit length\n\nAbout V & B\ni don't know any formulas that contain V & B \n\ni hope i could helped u