There are subatomic particles, which make up the atoms, namely protons, neutrons, and electrons. The electrons are negatively charged particles and move in varying directions within the atom. When the potential difference is applied to the end of a material, the electrons acquire some velocity which causes a small net flow in one direction. This velocity is the drift velocity, which we are explained below.
Drift velocity definition
Drift velocity is the average velocity, which is attained by any moving electron when an external electric field is applied to it. It is caused by the electrons when moved in one direction.
In a conductor, the free electrons move with different velocities in different directions. When an electric field is applied across the conductor, the electrons moving randomly experiences an electrical force in the direction of the field.
This causes the electrons to move randomly in motion and shifts towards higher potential with random motion. The electrons will drift towards the higher potential end of the conductor with random motions. We can so say that every electron will have a net velocity towards the end of the conductor with a higher potential. This velocity is the drift velocity of electrons.
Formula for drift velocity:
The average velocity gained by free electrons of a conductor is given by,
v = I/ nAq
Where, v is the drift velocity of electrons
I, the current flowing through the conductor
A, the area of cross-section of the conductor
q, the charge on an electron
n, the number of electrons
The SI unit can be given as, m/s and is measured in m² /(V.s)
What is the net velocity of electrons?
The materials which conduct like metal above absolute zero temperature, have some free electrons moving at random velocity. When we apply a potential around a conductor, the electrons tend to move towards the positive potential. They but finally will collide at some point and looses some of their kinetic energy. Due to the electric field, the electrons will continue to accelerate and random collisions will also continue. But, as the acceleration is in the same direction, the net velocity of the electrons will also be in the same direction.
