The mobility of free electrons charge -e- mass - m and-relaxation time - in a metal is proportional to -

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Standard XII

Physics

Drift Velocity

The mobility ...

Question

The mobility of free electrons (charge =e, mass = m and-relaxation time $τ$ ) in a metal is proportional to :

\frac{e}{m} τ

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\frac{m}{e} τ

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\frac{e}{m τ}

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\frac{m}{e τ}

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Solution

The correct option is D $\frac{e}{m} τ$
Drift velocity per unit electric field is called mobility of electron, i.e., $μ = \frac{V_{d}}{E} = \frac{E}{ρ n e E}$
Now, $ρ = \frac{m}{n e^{2} τ}$
$∴ μ = \frac{n e^{2} τ}{m n e} = \frac{e τ}{m}$

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The mobility of free electrons (charge =e, mass = m and-relaxation time τ) in a metal is proportional to :

The correct option is D emτDrift velocity per unit electric field is called mobility of electron, i.e., μ=VdE=EρneENow, ρ=mne2τ∴μ=ne2τmne=eτm

The mobility of free electrons (charge =e, mass = m and-relaxation time $τ$ ) in a metal is proportional to :

The correct option is D $\frac{e}{m} τ$
Drift velocity per unit electric field is called mobility of electron, i.e., $μ = \frac{V_{d}}{E} = \frac{E}{ρ n e E}$
Now, $ρ = \frac{m}{n e^{2} τ}$
$∴ μ = \frac{n e^{2} τ}{m n e} = \frac{e τ}{m}$