Define drift velocity and derive an expression for it

Apoorva Arora IIT Roorkee
8 years ago
Thedrift velocityis the flowvelocitythat a particle, such as an electron, attains due to an electric field. It can also be referred to as axialdrift velocity. In general, an electron will propagate randomly in a conductor at the Fermivelocity.
Malavika Sajeev
12 Points
7 years ago
Dreift velocity is the velocity attained by any particle such as electron when kept in an electric field.
Derivation:
Consider a cross section of conductor with length ‘l’ and area ‘A’. Let n be the no of electrons per unit volume.
The volume of conductor can be given as
V = Al
No. of electrons=nAl
Charge, q = ne= neAl
When connected with a battery current I pass through it which is equal to,
I = $\frac{q}{t}$ =$\frac{neAl}{t}$    $\because l/t=V$d
we can write this equation as:
I= enAVd
Malavika Sajeev
12 Points
7 years ago
Consider a conductor of length ‘l’. When electric field is applied, each electron experiances a force,
F= -eE ($\because$direction of force is opposite to direction of electric field)
It has an acceleration, $a=\frac{F}{m}$
i.e $a = \frac{-eE}{m}$
we know $v = a\tau$
$\therefore$ Drift velocity, $Vd = -\frac{eE}{m}\tau$
k.divakar k.divakar
36 Points
6 years ago
The volume of the conductor =Avdt=area×distance
Charge in that volume=Avdtne. Since ne=q
Now,Avdtne=q
Avdne=q/t=I

Luckyraj Rathore
17 Points
6 years ago
the average velocity with which free electrons drift under the influence of an external field. Vd = -eE r/m
Deepak
15 Points
5 years ago
electrons move with an average velocity which is independent of time although electrons are accelerated this is the phenomenon of drift and velocity Vis called drift velocity
3 years ago
Dear student,

The drift velocity is the flow velocity that a particle, such as an electron, attains due to an electric field. It can also be referred to as axial drift velocity. In general, an electron will propagate randomly in a conductor at the Fermi velocity.

Consider a conductor of length ‘l’. When electric field is applied, each electron experiances a force,
F = – eE ( F = qE, and q = – e)
Now, acceleration, a = F/m = – eE/m
Hence, v = u + aT = aT = – eE/m x T                      (assuming u = 0)
Hence, drift velocity, vd = – eET/m

Thanks and regards,
Kushagra