Drift Velocity

Introduction:

Drift Velocity has its influence on various topics in physics. This topic covers all the phases which find the difference with the properties of the Drift Velocity. The study further enhances the functioning of the electrons for the change in the electric charges. The types of velocity that it forms and its benefit in any electric circuit have the detaining overview in these notes.  

Definition:

Do you know what the meaning of drift is? To understand the Drift Velocity in physics, you have first to understand the meaning of drift. It is straightforward, as drift means slow movement of energy towards a particular direction. Similarly, in physics, the term Drift Velocity elaborates the average speed of the charged particles obtained when an electric force is applied. Typically, when the electric energy is not provided in a conductor, the electrons randomly occupy the Fermi Velocity, giving an average velocity of 0. However, with the occupancy of the charge in a small amount, the motion they ensure is further defined as the drift, which means they possess a slow movement. 

Apart from this, the Drift Velocity is highly proportional to the current; similarly, for a resistive material, these are also proportional to the magnitude of the external field.

Thus, we already understand that the Drift Velocity is defined as the slow heading of an object in a particular direction. However, the SI unit is written as m/s . 

However, according to Ohm’s Law, the Drift Velocity can be written as u =  µE. 

Here u is replaced with the Drift Velocity, 

µ is the mobility of the electron, and

E represents the electric current present in the field. 

The formula for Drift Velocity

Net Velocity of Electron: The electrons that remain present in the conductors usually move randomly without any proper direction, resulting in the collision among them. The flow of current can occur when they will not collide and move in a particular direction systematically. However, once they collide, the Net velocity of the electrons will perform the same. 

For instance, consider the first collision of electrons to be T1 , and then the second set of Electrons T2 will do the same and continue. Apart from this, if you consider the overall Net velocity of the electrons to be n that includes T1 – Tn, then the Formula for Drift Velocity in respect of Relaxation time is  (T) = (T1+T2+…Tn)/n

Also, we know that V = U + aT

Thus, we get that V representing the Net velocity of the electrons,

U is for the starting Velocity

a is for Acceleration, and lastly, T is the Time. 

Similarly, V = aT, and acceleration is a=F/m = -Ee/m 

Then the Drift Velocity =  Vd = – EemT

However, another Formula for Drift Velocity provides the relation among the Current and Drift Velocity, including I =  nAvQ. 

Similarly, here I represent the flow of the current that passes from the conductor and are also denoted as Amperes, 

A is the area that is obtained in the cross-sectioning of the conductor. This is further measured in m2:

On the other hand, n represents the overall amount of electrons, and v is the drift velocity. Lastly, the Q indicates the charge that can be measured in Coulombs.  

Therefore, drift velocity in simple words is the average velocity attained by electrons in the presence of an applied external electric field on the conductor.

Some things to consider are further listed below:

• The electrons present inside the conductor always have a random velocity, thus moving in a random direction. But when the charge is connected, it opts for the proper directional movement. 
• Also, the conductor’s presence further shifts from low to high potential end with the charge. 

What is the relation between the Drift Velocity and Current?

To understand the relationship between the Drift Velocity and current, you can consider the following example:

Drift Velocity and Current

Let’s assume L represents the conductor’s length,  A is the area of the Cross Section. Then you can find that the volume of the conductor is equal to A x L. 

Similarly, suppose n is equal to the number of electrons of the conductor per unit of its volume, then the total number of the same will be A x L x n. Then you can consider the electric charge  e present in an electron, which will be, however, similar to Q = ALne…. (1)

Now add a constant amount of difference of V to the ends of the conductor; you will notice the equation E = V/L. 

Now, the free electrons will start moving along with the Drift Velocity in this field. Then the time comes in, which gives t = L/vd…. (2). Also, current I = q/t….(3)

With the 1, 2, and 3, you will get  I = neAvd . 

However, as A, N, and E are constant, I is directly proportional to Vd. 

Conclusion:

These brief studies about the Drift Velocity and its various dimensions are shown in the conductor when the electric field is applied. This briefly explains the velocity of the conducts and the relation of the current and the drift velocity.