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(i) Define the term drift velocity. ...

(i) Define the term drift velocity.
(ii) On the basis of electron drift, derive an expression for resistivity of a conductor in terms of number density of free electron and relaxation time. On what factors does resistivity of a conductor depend ?
(iii) Why alloys like constantan and manganin are used for making standard resistors ?

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(iii) Alloys like constantan and manganin are used for making standard resistors because (a) their resistivity is comparatively higher, and (b) their temperature coefficient of resistivity is extremely small so that the resistance does not change with change in temperature.
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(i) Define the term drift velocity . (ii) On the basis of electron drift , derive an expression for resistivity of a conductor in terms of number density of free electrons and relaxation time. On what factors does resistivity of a coductor depend ? (iii) Why alloys like constantan and manganin are used for making standard restores ?

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Knowledge Check

  • If n,e,m and tau are free electron density in conductor , charge of electron and relaxation time of free electrons, then resistivity rho of the conductor can be expressed as .

    A
    `rho = (m)/("ne"^(2) tau)`
    B
    `rho = ("ne"^(2) tau)/(m)`
    C
    `rho = ("ne"^(2) tau)/(m)`
    D
    `rho = (m)/("ne" tau)`

  • If n ,e,m and tau are free electron density in conductor , charge of electron, mass of electron and relaxation time of free electrons , then resistivity rho of the conductor can be expressed as

    A
    `rho = ( m )/ ( n e^(2) tau ) `
    B
    ` rho = ( n e^(2) tau )/( m ) `
    C
    ` ( rho = ( n e tau )/( m ) `
    D
    ` rho = ( m )/( n e tau ) `

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