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Electromagnetic Devices

Table of Contents1 Scalar and vector fields.................................................................................................................12 Coulomb's law...............................................................................................................................33 Gauss law......................................................................................................................................54. PERMANENT MAGNET AND ELECTROMAGNET.............................................................85. BIOT-SAVART LAW...............................................................................................................116. AMPERE'S FORCE LAW........................................................................................................147. TOROIDAL COIL.....................................................................................................................16REFERENCES..............................................................................................................................20

1 SCALAR AND VECTOR FIELDSScalar fieldrefers to a quantity which has only magnitude. No direction is defined toscalar quantities. Scalar fields are addressed to be independent of coordinate system and sameunits will be observed from every direction. It also describes potential energy of physicalquantities defined with a specific force. Examples of scalar field which is used are temperature,pressure, higgs field. Scalar field is applied to many theories in physics which are illustratedbelow:·A scalar field combined with spin-0 particles in quantum field theory. Charged particlesare represented by scalar fields which is complex.·Scalar field is used to solve horizon problem. These are supposed to cause acceleratedexpansion of universe.·Scalar field is used to illustrate gravitation field.Vector fieldrefers to a quantity which has moth magnitude and direction. It is dependenton coordinate system and can be represented by arrows which shows both magnitude anddirection along with quantity.A force is represented as a vector quantity because a force is applied in a specific direction. Itcan be changed from one point to another point. Example of vector field are illustrated below:·Air movements can be represented with vector field on earth wind has both speed anddirection and can be visualised with an arrow.1

·A fluid which is moving is visualised as a vector quantity because it is associated withvelocity that is a vector quantity.Difference between scalar and vector fields are described below:Scalar fieldVector fieldIt has only magnitude.It has both magnitude and direction.It is one dimensional quantity.It is multidimensional quantity.It has simple comparison between twoquantities.It has complex comparison between twoquantities.Operations can be performed easily in scalarrepresentation.Operations can not be performed in vectorquantities.Vector fields are most complex one. Direction is represented by an arrow (Cooray,Rachidi and Rubinstein, 2017). In case of 3-D dimension, three unit vector are noted:·î is represented as unit vector in x- direction.·Ĵis represented as unit vector in y- direction.·K is represented as unit vector in z- direction.Length of arrow above quantity do not represent the size or length. It is a general representationof vector quantities.Lets explain scalar and vector field by taking an example:·a player who is playing football is running 20 miles per hour from starting to end. Is itscalar or vector?Solution: this is a vector field because it has magnitude of 20miles per hour and directionis given from starting to ending.·Temperature of room is observed to be 35 degree Celsius. Is it scalar or vector?Solution: this is a scalar because it has only magnitude. Temperature do not havedirection.·A force which is applied on a body which is shown by a point on Cartesian plane and ithas coordinates as (3,4). how can it is represented as vector form?Solution: a point (3,4)can be represented as f(x,y) = 3î + 4Ĵ .in this î and Ĵ are vector units which shows direction in x-plane and y- planerespectively.2

2 COULOMB'S LAWCoulomb's law is a law of physics which quantifies the amount of force either betweentwo stationary or electrically charged particles. A electrostatic force between two chargedelectrical bodies is called coulomb force. It is very important in theory of electromagnetism todiscuss quantity of electric charge. It generally gives an idea about force between two pointcharges.Therefore, Coulomb law states that “magnitude of electrostatic force of attraction orforce of repulsion between two charge points is directly proportional to product of magnitude ofcharges and inversely proportional to distance between two point charges”.Force of attraction or repulsion on the basis of above statement can be represented asF q1*q2∝F 1/ r∝F q1*q2/r∝hence it can be formulated as to calculate force of attraction or repulsion isF = k q1*q2/rhere,F = force of attractionq1, q2 = quantity of charge pointsr = distance between two charge pointsk = proportionality constant = ¼ π ε = 8.987551787 * 10₀ N. m.C ̃3

There are three conditions which needs to be assessed while considering coulomb's law:·charge should have spherical distribution symmetrically. It can be either point charges orcharged metal sphere.·Overlapping of charges should not be there.·Charges must be stationary with respect to each other.According to this law, charges with opposite signs attract each other and charges with same signrepel each other. Size of charges is small as compared to distance between toe charges. Thereforesize of charge is approximated as negligible (Halliday, Resnick and Walker, 2016). SI unit ofelectrostatic force is newton, distance is in metre and charges is in coulomb.Let's take examples to calculate coulomb force between two point charges.·Two charges of value 1C and -9C are kept at a distance of 9m. Find coulomb force andshow that it is attraction force or repulsion force.Solution : coulomb force can be calculated by formulae F = k q1*q2/rhere, F = 9*10 * 1*9/ 9F = 10 newton.As charges are of opposite sign,it represents that it is an electrostatic force of attraction.·Two point charges has a value of +3.37 μC and -8.21 μC. Force of attraction is given as0.0626 newton. Find the distance between two point charges.Solution: coulomb force can be calculated by formulae F = k q1*q2/r but here, distance needsto be calculated. So, by putting values in above formulae:0.0626 = 9*10 * 3.37* 8.21/ r= r = 9*10 * 3.37* 8.21/ 0.0626= r = sqrt (3.98)= r = 1.99 mCoulomb's law to find electrostatic force can be compared with gravitational forcebecause their point charges are replaced by mass of body. Distance between bodies or charges isinversely proportional to gravitational force or electrostatic force respectively.3 GAUSS LAWGauss law deals with study of electric charge and electric flux. It is applicable for closedsurface which has definite volume. Electric flux is defined as number of electric lines that goes4

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