- Drift Velocity Definition: Drift velocity is defined as the net velocity of free electrons moving randomly in a conductor due to an electric field.
- Random Electron Motion: Despite an electric field, electrons move randomly but drift towards the positive terminal, creating drift current.
- Drift Current: The consistent flow of electrons caused by drift velocity is known as drift current.
- Electron Mobility: Electron mobility (μe) is the ratio of drift velocity (ν) to the applied electric field (E), showing how easily electrons move through a conductor.
- Impact of Electric Field: A stronger electric field increases electron drift velocity, resulting in a higher drift current.
What is Drift Velocity?
Drift velocity is defined as the net velocity of free electrons moving randomly in a conductor due to an electric field. These electrons move at different speeds and directions. When an electric field is applied, they experience a force that aligns them towards the field direction.
This applied field, however, doesn’t curtail the random nature of electron motion. Instead, it compels them to gravitate towards higher potential while retaining their random motion. Consequently, the electrons drift towards the higher potential end of the conductor alongside their random movements.
This results in each electron acquiring a net velocity towards the conductor’s high potential end, referred to as the drift velocity of electrons.
The ensuing electrical current, due to this electron drift within an electrically stressed conductor, is termed the drift current. It’s worth noting that every electrical current is fundamentally a drift current.
The Relationship between Drift Velocity and Electron Mobility
Any conductive material, like metal, contains free electrons at room temperature. Scientifically, a conductive substance must have free electrons at temperatures above absolute zero.
Free electrons in the conductor move randomly, often colliding with atoms and changing direction.
When a steady electric field is introduced to the conductor, the electrons start gravitating toward the positive terminal of the applied electrical potential difference, commonly known as voltage. This electron movement, however, is not in a straight line.
As the electrons move toward the positive potential, they continuously collide with atoms and deflect randomly. Each collision results in a loss of some of their kinetic energy, which they regain due to the electric field’s influence, re-accelerating them towards the positive potential.
Further collisions lead to a similar loss and subsequent regain of kinetic energy. Therefore, while an applied electric field can’t halt the electrons’ random motion within a conductor, it does generate a net drift of electrons toward the positive terminal.
In simpler terms, the applied electric field causes the electrons to drift toward the positive terminal, giving them an average drift velocity. As the intensity of the electric field escalates, the electrons accelerate more quickly toward the positive potential post each collision. Consequently, the electrons gain more average drift velocity towards the positive potential, or in the direction opposite to the applied electric field.
Here, if ν represents the drift velocity and E symbolizes the applied electric field, electron mobility, denoted by μe, can be understood as the ratio of ν to E.
Where μe is referred to as electron mobility.
Drift Velocity, Drift Current, and Electron Mobility: An Animation
The constant movement of electrons due to drift velocity results in drift current.
Through clear understanding and further exploration, the interconnected concepts of drift velocity, drift current, and electron mobility can be appreciated for their critical roles in the world of electronics and physics.
The current caused by the steady flow of electrons due to drift velocity is called drift current.
