ev
Học thuậtThân thiện
Definition
Noun: A unit of energy, specifically an electronvolt. It is defined as the amount of kinetic energy gained or lost by a single electron when it accelerates through an electric potential difference of one volt.
Usage
The term ev (often capitalized as eV) is used as a standard unit of measurement in physics, particularly in atomic, nuclear, and particle physics, to express very small amounts of energy. - It is used to quantify the energy of particles, photons (like light), and in describing atomic-scale processes. - It is a compound unit, derived from the fundamental charge of the electron and the volt.
Examples
Advanced Usage
- Orders of Magnitude: Because the electronvolt is so small, prefixes are commonly used:
- keV (kilo-electronvolt): 1,000 eV
- MeV (mega-electronvolt): 1,000,000 eV
- GeV (giga-electronvolt): 1,000,000,000 eV
- TeV (tera-electronvolt): 1,000,000,000,000 eV
- Mass-Energy Equivalence: In particle physics, the eV is also used as a unit of mass via Einstein's equation E=mc². For example, the mass of an electron is approximately 0.511 MeV/c².
Variants and Related Words
- Electronvolt: The full, formal name for the unit.
- eV: The standard abbreviation (case-sensitive).
Synonyms
- There are no direct synonyms, as it is a specific, standardized unit. Related concepts include joule (the SI unit of energy, where 1 eV ≈ 1.602×10⁻¹⁹ joules).
Related Phrases/Contexts
- Ionization energy: Often measured in eV, it is the energy required to remove an electron from an atom or molecule.
- Band gap: In semiconductor physics, the energy difference between valence and conduction bands is expressed in eV.
- Rest mass energy: The intrinsic energy of a particle at rest, expressed in eV (or more commonly MeV/GeV).
Noun
- a unit of energy equal to the work done by an electron accelerated through a potential difference of 1 volt