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10/23/20101LECTURE 3: Carrier Action; Definitionof Current and Its componentsEECS 170A10/23/2010110/23/20102CURRENT CONDUCTION AND RESISTIVITY•In previous lectures we answered on how current was created where westarted with definition of current•After all current means #of charges passing per second. Hence, in order toconduct electrical current we need to transport carriers from one locationto other.•Carriers can move around by the effect of two different mechanisms:Diffusion or electromagnetic field, that generateDiffusion and Driftcurrents()FqEq vB•Diffusion subject will be covered after the review of drift current.•Let’s remember onDrift Currentinduced by electromagnetic field.•We said that under constant electric field, E, and magnetic field B, thecharged particle will expose to force F given by10/23/20103CURRENT CONDUCTION AND RESISTIVITY (2)•Electrons are active carriers which move around randomly. However, thenet displacement is 0 when there is no external force is present. Externalforces provide net displacement >0•In free space the motion of electron is uninterrupted•In lattice the motion of electrons are interrupted by collisionsEB***No magnetic fieldhol)es(where,are effective mass vales for electrons andnnpFqEdvFqmvEdqtBmmRandom walk E=0 , 0 displacement Directional movement E≠0CURRENT CONDUCTION AND RESISTIVITY (3)•What are these values at room temperature (it is temperature dependent!)10/23/20104**000001.180.810.550.360.0660.52npmmSimmGemmGaAsm
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