# Hall Effect

Hall effect is a process in which a transverse electric field is developed in a solid material when the material carrying an electric current is placed in a magnetic field that is perpendicular to the current. The Hall effect was discovered by Edwin Herbert Hall in 1879. In this article, let us learn about the Hall effect in detail.

## Principle of Hall effect

The principle of the Hall effect states that when a current-carrying conductor or a semiconductor is introduced to a perpendicular magnetic field, a voltage can be measured at the right angle to the current path. This effect of obtaining a measurable voltage is known as the Hall effect.

### Theory

When a conductive plate is connected to a circuit with a battery, then a current starts flowing. The charge carriers will follow a linear path from one end of the plate to the other end. The motion of charge carriers results in the production of magnetic fields. When a magnet is placed near the plate, the magnetic field of the charge carriers is distorted. This upsets the straight flow of the charge carriers. The force which upsets the direction of flow of charge carriers is known as Lorentz force.

Due to the distortion in the magnetic field of the charge carriers, the negatively charged electrons will be deflected to one side of the plate and positively charged holes to the other side. A potential difference, known as the Hall voltage will be generated between both sides of the plate which can be measured using a metre.

The Hall voltage represented as VH is given by the formula:

$$\begin{array}{l}V_H=\frac{IB}{qnd}\end{array}$$

Here,

I is the current flowing through the sensor

B is the magnetic field strength

q is the charge

n is the number of charge carriers per unit volume

d is the thickness of the sensor.

### Hall Coefficient

The Hall coefficient RH is mathematically expressed as

$$\begin{array}{l}R_H=\frac{E}{jB}\end{array}$$

Where j is the current density of the carrier electron, Ey is the induced electric field and B is the magnetic strength. The hall coefficient is positive if the number of positive charges is more than the negative charges. Similarly, it is negative when electrons are more than holes.

#### Applications of Hall Effect

Hall effect principle is employed in the following cases:

• Magnetic field sensing equipment
• For the measurement of direct current, Hall effect Tong Tester is used.
• It is used in phase angle measurement
• Proximity detectors
• Hall effect Sensors and Probes
• Linear or Angular displacement transducers
• For detecting wheel speed and accordingly assist the anti-lock braking system.

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## Frequently Asked Questions – FAQs

Q1

### Name one practical use of Hall effect.

Hall effect is used to determine if a substance is a semiconductor or an insulator. The nature of the charge carriers can be measured.

Q2

### How is Hall potential developed?

When a current-carrying conductor is in the presence of a transverse magnetic field, the magnetic field exerts a deflecting force in the direction perpendicular to both magnetic field and drift velocity. This causes charges to shift from one surface to another thus creating a potential difference.

Q3

### What is a Hall effect sensor?

A Hall effect sensor is a device that is used to measure the magnitude of a magnetic field.

Q4

### In the Hall effect, the direction of the magnetic field and electric field are parallel to each other. True or False?

False. The magnetic field and electric field are perpendicular to each other.

Q5

### Explain Lorentz Force.

Lorentz force is the force exerted on a charged particle q moving with velocity v through an electric field E and magnetic field B.

Watch the video to understand how a magnetic field is created by a current-carrying conductor.

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