2Coordinate SystemsThe physical quantities in EM are vector fields which are functions of space and time. To describe the variations of the quantities in space, we need a suitable coordinate system.Laws of electromagnetism are “invariant” with the chosen coordinate system.A point in 3D space can be specified as the intersection of 3 surfaces.u1= const.u2= const.u3= const.u’smay be lengths or angles.When these 3 families of surfaces are mutually orthogonal (perpendicular) to each other, we have an “orthogonal coordinate system”.
3Orthogonal Coordinate Systems3 PRIMARY “ORTHOGONAL”COORDINATE SYSTEMS:•CARTESIAN•CYLINDRICAL•SPHERICALChoice is based on symmetry of problemExamples:Sheets - CARTESIANWires/Cables - CYLINDRICALSpheres - SPHERICALHow do we choose a suitable coordinate system?
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