When an electric current is passed through a conductor by placing it perpendicular to a magnetic field, then a voltage is generated on both sides of that conductor. The phenomenon of generation of voltage in the conductor is called Hall Effect.
The Hall Effect was named after its discoverer, Edwin Hall. This is somewhat similar to Fleming’s right-hand rule. When a current carrying conductor I is placed in a transverse magnetic field B, an electric field E is induced in the conductors perpendicular to both I and B. This phenomenon is called the Hall Effect.
Principle of Hall Effect
When the electric circuit is completed by connecting a conductor to the power source (battery etc.), then the current starts flowing from the power source. The flow of electric current in a conductor is due to charge carriers (electron holes or ions). When this conductor is kept perpendicular to a magnetic field, then these charge carriers start experiencing a force on themselves.
This force experienced by the charge carrier is called Lorenz force. Due to this force, negatively charged electrons move opposite to the force and positively charged holes start gathering on the surface of the conductor. Due to the accumulation of charge carriers on the surface, a voltage is generated between the two surfaces. The voltage generated between the two surfaces is called the Hall Voltage and is determined by the following formula:
Where:
VH = Hall Voltage.
I = Current flowing through the conductor.
B = Magnetic field intensity.
d = conductor width.
Q = Quantity of charges.
N = Number of charges in unit volume.
Hall Effect Sensor
It is a type of electronic device that detects a magnetic field, that is, it is used to sense a magnetic field. Since it works on the principle of the hall effect, it is called Hall Effect Sensor.
Explanation of Hall Effect Sensor
When a current carrying conductor is placed in a transverse magnetic field, this magnetic field exerts some pressure on the electrons which take a curved path to continue their journey. The conductor with the applied energy is shown in the following figure. The magnetic field is also indicated.
As electrons travel through a conductor located in magnetic field B, the electrons will experience a magnetic force. This magnetic force will cause the electrons to travel closer to one side than the other. This creates a negative charge on the one hand and a positive charge on the other, as shown in the following figure:
This separation of charge will create a voltage difference known as Hall voltage or Hall emf. The voltage builds up until the electric field produces an electric force on the charge equal and opposite to the magnetic force. This effect is known as the Hall effect.
VD is the velocity that each electron is experiencing
where q = quantity of charge
d = distance between planes in a conductor
Uses of Hall Effect
The Hall effect is used to obtain information such as semiconductor type, sign of charge carriers, electron or hole concentration, and measure mobility. From there, we can also know whether the material is a conductor, insulator or semiconductor. It is also used to measure the magnetic flux density and strength in an electromagnetic wave.
Types of Currents
For the types of currents in semiconductors, two terms need to be discussed. They are Diffusion Current and Drift Current.
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Diffusion Current
When doping is done, there is a difference in the concentration of electrons and holes. These electrons and holes diffuse from the higher concentration of charge density to the lower concentration level. Since they are charge carriers, they produce a current called diffusion current.
To know about this in detail, let us consider an n-type material and a p-type material.
- N-type materials have electrons as majority carriers and few holes as minority carriers.
- P-type materials have holes as majority carriers and few electrons as minority carriers.
If these two substances are brought too close to each other to connect, some electrons from the valence band of the n-type material will move from the valence band of the p-type material and some holes will move from the valence band of the p-type material. Huh. walk towards. N-type material. The region between these two substances where this diffusion occurs is called the depletion region.
Therefore, the current formed due to diffusion of these electrons and holes without the use of any kind of external energy can be called as diffusion current.
Drift Current
The flow of electrons of charged particles or the current formed due to holes due to the applied electric field is called drift current. The following figure explains the drift current, regardless of how the applied electric field makes a difference.
The amount of current flowing depends on the charge applied. The width of the weathering zone is also affected by this runoff current. For a component in an active circuit to function, this drift current plays an important role.