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NEET UG 2026 » NEET UG Study Material » Physics » FERMI EQUATION
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FERMI EQUATION

At absolute zero temperature, the Fermi energy is the energy difference between the highest and lowest populated single-particle states in some kind of a quantum system of non-interacting fermions

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The Pauli exclusion principle governs a group of particles known as fermions (for example, electrons, protons, and neutrons) in quantum mechanics. This means that two fermions cannot be in the same quantum state at the same time. We may claim that two fermions would occupy the same stationary state because an idealised non-interacting Fermi gas can be analysed in terms of single-particle stationary condition. In most cases, the energy of these stationary states will be different. We start with an empty system and add particles one at a time, sequentially filling up the unoccupied immobile states with the lowest energy to identify the system’s ground state. The Fermi energy is the kinetic potential of the highest occupied state after all the particles have been added.

THEORY

The idea of energy is difficult to grasp in physics since it has many meanings depending on the situation. Light energy, electrical energy, heat energy, and other types of energy exist in atoms and molecules, for example. It gets considerably difficult in quantum mechanics. Scientists use notions like Fermi energy, which refers to the energy of the maximum occupied quantum state in a system of fermions at absolute zero temperature, in this discipline of physics.

What is Fermi Energy

A Fermi level, named after physicist Enrico Fermi, is a measurement of the energy of the least securely confined electrons within a material. It’s crucial for determining solids’ thermal and electrical properties.

The Fermi energy is the value of the Fermi level at absolute zero temperature (273.15 °C). It’s also the greatest kinetic energy an electron can have at zero degrees Celsius. Each solid has a constant Fermi energy.

The words Fermi level and Fermi energy are frequently used interchangeably and might be confusing. Despite the fact that both terms are equal at absolute zero, they are not the same at other temperatures.

The Fermi energy is used to calculate the electrical and thermal properties of solids. It’s a key idea in both superconductor thermodynamics and quantum mechanics. It’s employed in insulators and semiconductors.

What is Fermi Level, and what does it mean?

The Fermi Level is the maximum energy level that an electron can reach at absolute zero temperature. Because all electrons are in the lowest energy state at absolute zero temperature, the Fermi level falls between the valence and conduction bands. The Fermi level can be thought of as a sea of fermions (or electrons) above which no electrons exist due to a lack of energy at 0 Kelvin. As the solids are heated and electrons are added to or removed from them, the Fermi level changes.

Energy Level of Fermi

Because of Pauli’s exclusion principle, which stipulates that two fermions cannot occupy the same quantum state, this energy level exists. As a result, if a system contains more than one fermion, each fermion has its own set of magnetic quantum numbers.

The Fermi Temperature is equal to the Fermi level’s energy divided by Boltzmann’s constant. The temperature at which the electron’s energy equals the Fermi energy is also known as the Fermi temperature. It’s a measurement of the electrons in a metal’s lower energy states.

Fermi Energy’s Applications

In quantum mechanics and condensed matter physics, it is one of the most essential notions. The following sections discuss several Fermi energy applications.

  • It’s employed in insulators and semiconductors.
  • Insulators, metals, and semiconductors are all described by this term.
  • The Fermi energy is used to calculate the electrical and thermal properties of solids.
  • Understanding the stability of white dwarfs is very crucial in nuclear physics. White dwarfs are stars with a mass similar to the Sun but a radius less than a hundredth of the Sun’s.

CONCLUSION

At absolute zero temperature, the Fermi energy is the energy difference between the highest and lowest populated single-particle states in some kind of a quantum system of non-interacting fermions. The idea of energy is difficult to grasp in physics since it has many meanings depending on the situation. Light energy, electrical energy, heat energy, and other types of energy exist in atoms and molecules, for example. It gets considerably difficult in quantum mechanics

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Frequently Asked Questions

Get answers to the most common queries related to the NEET UG Examination Preparation.

What is the energy level of Quasi-fermi?

Answer: The change in Fermi level as charge carriers are introduced excessively to the semiconductor is known as the...Read full

When p-type and n-type semiconductors are combined, what happens to the Fermi energy level?

Answer: The Fermi energy level falls for n-type and increases for p-type until...Read full

When a forward bias is applied to a PN junction diode, what happens to the Fermi energy level?

Answer: When a forward bias is applied, the Fermi energy level of the n-type increases, whereas the Fermi energy lev...Read full

When a reverse bias is applied to a PN junction diode, what happens to the Fermi energy level?

Answer: In the event that a reverse bias is applied, the Fermi energy level for n-type decreases while it increases ...Read full

What is the process of earthing?

Answer: It is accomplished by connecting the equipment’s neutral or non-current carrying portion to the ground...Read full

Answer: The change in Fermi level as charge carriers are introduced excessively to the semiconductor is known as the quasi-fermi energy level.

Answer: The Fermi energy level falls for n-type and increases for p-type until equilibrium is reached.

Answer: When a forward bias is applied, the Fermi energy level of the n-type increases, whereas the Fermi energy level of the p-type falls.

Answer: In the event that a reverse bias is applied, the Fermi energy level for n-type decreases while it increases for p-type.

Answer: It is accomplished by connecting the equipment’s neutral or non-current carrying portion to the ground.

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