Knowra Electronvolt Electronvolt The electronvolt (eV) is a unit of energy equal to the energy gained by an elementary charge moving through a potential difference of one volt: approximately 1.602 × 10⁻¹⁹ joules.
Elementary charge : The magnitude of the electric charge of a proton or electron, approximately 1.602 × 10⁻¹⁹ coulombs. Multiplying this charge by one volt gives the electronvolt in joules.
Particle physics : The study of the fundamental particles of matter and the forces between them. Particle masses and collision energies are commonly reported in electronvolts and their multiples.
Electronvolt per particle : An energy value expressed for each individual particle rather than for a macroscopic amount of substance. An electronvolt is an energy unit; attaching “per particle” specifies how an energy value is allocated.
Electronvolt–joule conversion : The exact conversion of one electronvolt to joules, fixed by the elementary charge in SI units. Since the 2019 SI redefinition, the elementary charge fixes the conversion exactly at 1.602176634 × 10⁻¹⁹ joules.
Electric potential difference : The change in electric potential energy per unit charge between two points, measured in volts. An electronvolt is the energy associated with one volt of potential difference across an elementary charge.
Atomic physics : The study of atoms, including their structure, interactions, and energy levels. Atomic excitation and ionization energies are naturally expressed in electronvolts.
Electronvolt per kelvin : A unit of energy divided by temperature, used for quantities such as Boltzmann’s constant. It differs from the electronvolt because the additional kelvin denominator changes the physical dimension.
Electronvolt as a unit of mass : The use of energy units to express mass through the relation E = mc². In particle physics, mass is often written in eV/c², or expressed as energy when c is set to one.
Joule : The SI unit of energy, equal to one kilogram metre squared per second squared. The joule is the SI unit used to express the electronvolt’s exact conversion value.
Photon energy : The energy carried by a photon, determined by its frequency or wavelength. Visible-light photons have energies of a few electronvolts, making the unit useful in spectroscopy.
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