Definition of drift velocity
If a particle moves in space so that it randomly changes its directions and velocities, the result of these random movements together is called drift velocity.
The definition of drift velocity can be understood by imagining the free random motion electrons in a conductor. Free electrons move in a driver at random speeds and directions. When we apply an electric field to the conductor, the random electrons are subject to an electric field force.
Because of this field, the electrons do not give up their random motion but change their random motion to a higher potential. This means that the electrons drift to a higher potential with their random movements. Thus, each electron has a net velocity towards the higher potential end of the conductor, and we call this net velocity the drift velocity of the electrons. When hopping, you understand the definition of the drift speed. The current due to this movement of electron drift in a live conductor is called drift current. Of course, every electric current is a “drift current”.
Drift speed and mobility
In each metal, free electrons are always present at room temperature. Scientifically, at least some free electrons must be present at any temperature above absolute zero when the substance is conductive, e.g. B. a metal. These free electrons within the conductor move randomly and often collide with heavier atoms, changing direction each time. When a constant electric field is applied to the conductor,
the electrons move toward the positive terminal of the applied electric potential difference. However, this movement of the electrons does not take place directly.
On the way to the positive potential, the electrons constantly collide with the atoms and bounce off arbitrarily. During the collision, the electrons lose part of their kinetic energy and are accelerated back to
the positive potential due to the presence of an electric field and regain their kinetic energy. Even with subsequent collisions, the electrons partially lose their kinetic energy in the same way. Thus, the applied electric field can not stop the random movement of electrons within a conductor. Although the movements of the electrons remain random in the presence of the applied electric field, this leads to a global movement of the electrons towards the positive terminals.