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Using the concept of free electrons in a conductior , derive the expression for the conductivity of a wire in terms of number density and relaxation time . Hence obtain the relation between current density and the applied electric field E. |
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Answer» Solution :Derivationof the expression for conductivity Relation between density and electric field The acceleration ` OVERSET to ( a) = - ( in )/( m ) oversetto E ` The average drift velocity , vd, is given by ` vd = - ( eE) /( m ) ` ` ( TAU `=average time betweencollisions / relaxtion time ) If n is the number of free ELECTRONS per unit volumes , the current I is given by ` I= neA | vd| ` = ( e^(2) A)/( m ) tau n |E| ` But I= |J| A ( j = current density ) we . THEREFORE . get |
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