Question

When a steady current flow through a conductor the electron in it move with a certain average drift speed.

Explain these lines ​

Answer 1

Answer:

The average velocity of all the free electrons in the conductor is called the drift velocity of free electrons of the conductor. When a conductor is connected to a source of emf an electric field is established in the conductor, such that E=LV

When V= potential difference across the conductor and L=length of the conductor 

The electric field exerts an electrostatics force '−Ee' on each free electron in the conductor 

The acceleration of each electron is given by 

aˉ=−meE

Where, e=electric charge on the electron and 

m=mass of electron 

Acceleration and electric field are in opposite directions, so the electrons attain a velocity in addition to thermal velocity in the direction opposite to that of electric field. 

vd=mcEτ...............(i)

E=L−V...........(ii)

Where τ=relaxation time between two successive collision 

Let n=number density of electrons in the conductor 

N0. of free electrons in the conductor =nAL

Total charge on the conductor , q=nALe

Time taken by this charge to cover the length L of the conductor,

t=vdL

Current I=tq

=LnALe×vd

=nAevd

Using equation (i) and (ii), we get that 

I=nAe×(−mLe(−V)τ)

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