chapter5-Electric Fields in material space-Fall 2015-V1.pdf...

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Electromagnetics[email protected]ElectromagneticsElectric Fields in Material SpaceCurrents, Conductors, Polarization
Electromagnetics[email protected]Questions – I What does current mean and what makes current flow in conductors ? 2015-09-21Electric fields in material 2
Electromagnetics[email protected]Questions – II Will the electric fields will be the same in materials as in empty space? What does Polarization in dielectric materials mean? And how much is its importance in electromagnetics? 2015-09-21Electric fields in material 3
Electromagnetics[email protected]Questions – IIIIf the electric field exists in a region consisting of two different media, the electric field will show the same characteristics in two different media? If the electric field shows different characteristics in two media, how we can link different characteristics at the interface separating the media in order to satisfy the continuity nature? 2015-09-21Electric fields in material 4
Electromagnetics[email protected]TopicsElectric Field in Material Space (Chap. 5)Material PropertiesConvection and Conduction CurrentsConductorsPolarization in Dielectrics2015-09-21Electric fields in material 5
Electromagnetics[email protected]Electrical Properties of MaterialsMaterials are broadly classified asConductors (σ >>1)Dielectrics (Insulators) (σ <<1)SemiconductorsConductors have an abundance of free electronsDielectrics have few free electronsMajor difference is the number of electrons available for conduction of currentPerfect conductor (σ= )Perfect dielectrics (σ= 0)2015-09-21Electric fields in material 6
Electromagnetics[email protected]Conductors and DielectricsSome material are conductors and some are dielectrics……2015-09-21Electric fields in material 7
Electromagnetics[email protected]DefinitionThe current (in amperes) through a given area is the electric charge passing through the area per unit time.Current in dielectrics is generally called as convection current.A beam of electrons in a vacuum tubeCurrent in conductors is generally called as conduction current.Current is a rate of change of electric charge.Current – I (5.1)[A]dtdQI=2015-09-21Electric fields in material 8
Electromagnetics[email protected]DefinitionIf current Iflows through a planar surface, the current density J [A/m2] is If the current density is not normal to the surface, Thus total current flowing through a surface SisCurrent – II SJISIJ==or (5.3)SJ=I(5.4)S=SJdI2015-09-21Electric fields in material 9
Electromagnetics[email protected]Current – IIIExample 5 -1 [Text Practice 5.1]If J= 10z sin2φaρA/m2, find the current through the cylindrical surface ρ= 2, 1 z5m.

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