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Every substance is made up of atoms consisting of negatively charged electrons. Within the atom, these negatively charged electrons move in a random pattern. The movement of electrons results in the generation of electricity. However, electrons in a material have a zero average velocity because of their random motion.
Drift velocity refers to the velocity of the electrons that causes them to move in a particular direction. Like metals above absolute zero temperature, each material that can lead has a few free electrons moving indiscriminately at speed.
What is the Definition of a Drift Velocity?
Drift velocity is the normal speed achieved by haphazardly moving electrons when an outside electric field is applied, making the electrons move in a single direction.
Every conductor material has free, randomly moving electrons at temperatures above absolute zero temperature. Whenever an outside electric field is applied to a material, they tend to move positively, resulting in a net velocity of electrons in one direction. The electron will move towards the electric field that has been applied. In this case, the electron does not abandon its randomness of motion but rather shifts to a higher potential with its irregular movement.
Drift current is the current produced by the movement of electrons towards higher potential. As a result, any current produced in a conductor material can be classified as a drift current.
The Formula of Drift Velocity
The normal speed acquired by free electrons in a guide is given by,
V = I/Q
Where v signifies electron drift speed and I is the constant current through the conductor.
How fast do electrons travel in a straight line?
Some free electrons move at random velocity in materials that lead like metal above absolute zero temperature. Electrons tend to gravitate towards the positive potential when a potential is applied to a conductor. They will eventually collide with atoms and some of their kinetic energy will be lost. Electrons will continue to accelerate due to the electric field and randomly collide with atoms. However, because the electrons’ speed increase is in the same direction, their net speed will be in a similar direction.
The Drift Velocity-Electric Current Relationship
Every conductor contains free electrons that move randomly. A current is generated by the movement of electrons in one direction caused by the drift velocity. The drift velocity of the electrons is typically in the range of 10-1 m/s. An electron will typically take 17 minutes to pass through a one-metre-long conductor with this amount of velocity.
If we turn on an electric bulb after 17 minutes, it should light up. However, with the flick of a switch, we can turn on an electric light bulb in our home in record time. This is because the speed of an electric current is independent of the electron’s drift velocity.
The speed of light is the speed of the electric current. It has nothing to do with the electron drift velocity in the material. Thus, the speed of electric current may vary depending on the material, but the speed of light always determines it.
Drift Velocity’s Expression
When the mobility of the charge carriers and the strength of the applied electric field E are known, Ohm’s law can be expressed in terms of drift velocity as
vD=eVt/ml
Electron mobility is measured in S.I. units of m2/V-s.
Electric field e is measured in S.I. units of V/m.
As a result, v’s S.I. unit is m/s. Axial drift velocity is another name for this S.I. unit.
Example
Question
A copper wire’s cross-section area is 7.85 x 10-7 m2. Copper has an atomic number density of 8.5 x 1028 m-3. When the current is 1.4 A, compute the mean drift velocity of electrons through the wire. (3 points)
Answer:
As is well known,
nAve + nAve + nAve + nAve
As a result, the drift velocity = v = I/. (nAe)
7.85 x 10-7 m2 A = 7.85 x 10-7 m2 A = 7.85 x 10-7
8.5 x 1028 m-3 is the unit of measurement.
And I equal 1.4 A
E = 1.6 x 10-19 is well known.
As a result, v = 1.4 / (8.5 x 1028 * 7.85 x 10-7 * 1.6 x 10-19).
1.31 x affirmative m/s is the speed.
Conclusion
When no external electric field is applied, electrons in the conductor move at random. Because the net velocity of the electrons produced by them is cancelled due to random collide with atoms, the net current is zero. As a result, the relationship between electric current, current density and drift velocity aids in the proper flow of electric current through the conductor. We can deduce from the preceding formula that current density is proportional to an electron’s drift velocity. Metals with free electrons move at absolute zero temperature. Drift velocity is a vector quantity because it requires both magnitude and direction.
