The Jargon

We know that two charged bodies  either attract or repel each other. Like charges repel each others and unlike charges attract each others.  Coulomb’s Law attempts to define the force that is exerted when the two bodies are attracted or repelled because of their charges. Coulomb’s Law states that: The force exerted between two stationary point charges: i. Is directly proportional to the product of charge strength of the two charges. ii. Is inversely proportional to the square of distance between the two charges. Mathematically the Coulomb’s law can be represented as:                    and                         Where, F = Force of attraction between the two particles ,Q1 = charge of first particle , Q2 = charge of second particle and r = distance between the two particles. Combining equation i and ii we get: Now if we replace the proportionality by the constant of proportionality (K ) then we get: The constant of proportionality (K ) is called the Dielectric Constant and given as : W

Materials contain charged particles that under the application of external fields respond giving rise to three basic phenomena known as conduction, polarization, and magnetization. Conduction: Conduction is the phenomenon whereby the free electrons inside the material move under the influence of the externally applied electric field with an average velocity proportional in magnitude to the applied electric field. the conduction current density, is measured in amperes per square meter (A/m 2 ). J C = σ E σ is the conductivity of the material units are Siemens per meter (S/m). J is the current density.   Polarization:           Polarization is the phenomenon of creation and net alignment of electric dipoles, formed by the displacements of the centroids of the electron clouds of the nuclei of the atoms within the material, along the direction of an applied electric field. relationship between D and E, which is given by D = εΕ . considering polarization in to account electric

The force acting on a charge moving in an electromagnetic field, as given by the Lorentz force is associated two field vectors electric flux density(D) and the magnetic field intensity(H). Electric flux density (D): Electric flux is the normal (Perpendicular)  flux per unit area. If a flux of  passes through an area of  normal to the area then the flux density ( Denoted by D) is: If a electric charge is place in the center of a sphere then the electric flux on the surface of the sphere is: , where r =radius of the sphere. The SI unit of electric flux is Coulomb per meter square. Relation between Electric flux density and electric field intensity: If we compare the formula for the Electric flux Density given above with the formula for the Electric Field intensity ,  We see that:   and   Where , = Permittivity of vacuum and   = relative Permittivity. Thus, We can conclude that:       And,      

Maxwell equations: The electric and magnetic fields are governed by a set of four laws, known as Maxwell’s equations. Maxwell’s equations form the basis for the entire electromagnetic field theory. Max well’s equations in integral form: 1. Faraday’s law:                         A time-varying magnetic field gives rise to an electric field. Specifically, the electromotive force around a closed path C is equal to the negative of the time rate of increase of the magnetic flux enclosed by that path, that is,      2. Ampere’s circuit law: Time varying electric fields give rise to magnetic fields. Specifically, the magnetomotive force (mmf) around a closed path C is equal to the sum of the current enclosed by that path due to actual flow of charges and the displacement current due to the time rate of increase of the electric flux (or displacement flux) enclosed by that path; that is,         3. Gauss law of electric field: Gauss’ law for the electric field states that electric charges give

  Lorentz Force Equation   The force experienced by current element in magnetic field is given as sum of force due to electric field and magnetic field.   Force due to electric field: A region is said to be characterized by an electric field if a particle of charge q moving with a velocity v experiences a force Fe, independent of v. The force, Fe, is given by              F e = qE ---------------------------------------- (1.1)                    E is the electric field intensity. Measured in newtons per coulomb (N/C) or volts per meter. Where volt is a newton-meter per coulomb. The line integral of E between two points A and B in an electric field region gives voltage between A and B. It is the work per unit charge done by the field in the movement of the charge from A to B. Force due to magnetic field: If a charged particle experiences a force which depends on v, then the region is said to be characterized by a magnetic field. The force, Fm, is given by                     F m =qv *