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Drift velocity is the average speed of charged particles in a material when influenced by an electric field. It refers to their slow movement toward an object. Let’s explore drift velocity further in this article.
What is Drift Velocity?
The average velocity of the free electrons in a conductor when an electric field is applied is known as drift velocity. It is much smaller than the velocity of light. The unit of drift velocity is meters per second. The drift velocity is directly proportional to the electric field strength and inversely proportional to the relaxation time of the electrons.
The drift velocity is important because it is the velocity at which charge carriers move through a conductor, which determines the current through the conductor.
Formula of Drift Velocity
The formula used to calculate drift velocity is as follows:
I = nAvQ
v = I / nAQ
Where,
- I = Current flowing from the conductor in Amperes
- n = Number of electrons
- A = Area of the cross-section of a conductor in m2
- v = Drift velocity of electrons
- Q = Charge of electron in Coulombs
Example:
Consider a current of 5A which is following in a copper conductor with a cross-section of 1mm2.
We know that the number of electrons (n) in copper is 8.5 x 1028 per m3.
As per the formula,
5 = 8.5 × 1028 × 1 10-6 × v × 1.6 × 10-19
Where Q is 1.6 x 10 -19 C
So, v = 5 / 8.5 × 1028 × 10-6 × 1.6 × 10-19
v = 5.89 × 10-4 ms-1
When the electric field’s intensity increases, electrons experience a stronger force, causing them to accelerate faster in the opposite side of the applied electric field, moving towards the positive direction.
Relation between Current and Drift Velocity
The drift velocity is a concept related to the movement of charged particles (such as electrons) in a conductor when the electric current flows through it. When an electric field is applied to a conductor, it exerts a force on the charge carriers, causing them to move in response. The drift velocity represents the average velocity of these charge carriers as they move through the conductor.
The relation between drift velocity and electric current is that the drift velocity is directly proportional to the electric current. In other words, as the electric current increases, the drift velocity of the charge carriers also increases. This relationship is described by the equation:
Drift Velocity ∝ Electric Current
Factors such as the material of the conductor and the strength of the applied electric field can influence the drift velocity of charge carriers in a given situation. The concept of drift velocity helps us understand how charges move through conductors and is fundamental in the study of electrical conductivity and current flow in circuits.
Relation between Drift Velocity and Current Density
Current density is the measure of how much electric current flows through a specific area of a conductor in a given time. It tells us how concentrated the current is in a particular part of the conductor.
We know that the formula for drift velocity is:
I = nAvQ
J = I / A = nVQ
Where,
- J is the current density measured in Ampere per meter square
- V is the drift velocity of the charged particles
The drift velocity of electrons and the current density are directly related, meaning they increase together. When the electric field intensity rises, both the drift velocity and the current flowing through the conductor increase as well. These relationships are fundamental in understanding how electric current behaves in a conductor.
Frequently Asked Questions on Drift Velocity
What is meant by drift velocity?
Drift velocity is generally defined as the average velocity attained by charged particles (e.g., electrons) in a material due to an electric field. The SI unit of drift velocity is a meter per second.
What determines drift velocity?
Drift velocity is determined by the strength of the applied electric field and the material's properties, such as conductivity and charge carrier mobility. These factors influence the speed of charged particles' movement.
What is the relationship between current and drift velocity?
The current is directly proportional to the drift velocity of charged particles. When drift velocity increases, the current in the conductor also increases, reflecting the relationship between the two.
