- Derive an expression for drift velocity of free electrons.
- How does drift velocity of electrons in a metallic conductor vary with increase in temperature? Explain.
CBSE OUTSIDE DELHI - SET 3 CENTRAL 2016
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- When a potential difference is applied across a conductor, an electric field is produced, and free electrons are acted upon by an electric force $( = - \text{E}e ) .$ Due to this, electrons accelerate and keep colliding with each other and acquire a constant (average) velocity $\text{v}_{d}.$
$\therefore\text{F}_{e} = \frac{-\text{eV}}{l}$
As $\text{a} = \frac{-\text{F}}{\text{m}} = \frac{- \text{eV}}{\text{m}}$
as v = u+at
u = 0 , $\tau$= (relaxation time)
$\text{v}_{d} = \text{- a }\tau $
$\text{v}_{d} = \frac{ -\text{eV}}{l\text{m}}\tau$
- Decreases, as time of relaxation decreases.
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