Electronvolt
Unit of energy gained by an electron through one volt.
The electronvolt (symbol eV) is a unit of measurement equivalent to the amount of kinetic energy gained by a single electron accelerating through an electric potential difference of one volt in a vacuum. It is a commonly used unit of energy within physics, widely used in solid state, atomic, nuclear and particle physics, and high-energy astrophysics.
- field
- Physics
- unit_type
- Energy
- symbol
- eV
- common_prefixes
- meV, keV, MeV, GeV, TeV, PeV, EeV, ZeV, YeV, ReV, QeV
- related_units
- eV/c² (mass), eV/c (momentum)
Lore & Background
Historically, the electronvolt was devised as a standard unit of measure through its usefulness in electrostatic particle accelerator sciences, because a particle with electric charge q gains an energy E = qV after passing through a voltage of V. The electronvolt is not an SI unit but is commonly used with SI prefixes such as milli-, kilo-, mega-, giga-, tera-, peta-, exa-, zetta-, yotta-, ronna-, and quetta-.
Reader's Guide
The electronvolt is a fundamental unit in modern physics, enabling convenient expression of energies at atomic and subatomic scales. Its definition ties directly to the elementary charge and the volt, making it intuitive for describing particle accelerators and quantum phenomena. Similarly, momentum is often expressed in eV/c. The unit's flexibility with SI prefixes allows it to span from milli-electronvolts (meV) in solid-state physics to quetta-electronvolts (QeV) in high-energy astrophysics. Its adoption in the 2019 SI revision as an exact value ensures precision in calculations across disciplines.
Did You Know?
- The electronvolt is not an SI unit but is widely used in physics.
- In some older documents, the symbol BeV (billion electronvolt) is used, equivalent to GeV.
Frequently Asked Questions
What exactly is an electronvolt?
It is the kinetic energy a single electron acquires when it is accelerated across a one-volt potential difference in a vacuum. Physicists and chemists use it as a compact energy unit spanning atomic, nuclear, solid-state, and high-energy astrophysics contexts.
What prefixes do people actually pair with eV?
The full ladder runs from meV (milli) up through keV, MeV, GeV, TeV, PeV, EeV, ZeV, YeV, ReV, and QeV. In practice, particle physicists gravitate toward GeV and TeV, while solid-state and atomic researchers tend to stay in the meV-to-keV range.
Why do chemists reach for eV instead of joules?
Bond dissociation energies, ionization potentials, and semiconductor band gaps land at tidy one- or two-digit values when expressed in eV. That makes comparisons and calculations far more intuitive than juggling 10⁻¹⁹-joule figures.
Can eV express mass or momentum as well?
Yes—dividing an energy by c² yields a mass in eV/c², and dividing by c gives a momentum in eV/c. This shorthand is standard in particle physics, where quoting kilograms or kg·m/s would produce absurdly small numbers.
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