Electronvolts to Joules Converter

How to Convert Electronvolts to Joules

Converting electronvolts (eV) to Joules (J) is a fundamental operation in particle physics, quantum mechanics, semiconductor engineering, and materials science. The electronvolt is a unit of energy defined as the kinetic energy gained by a single electron when it accelerates through an electric potential difference of one volt. It is the preferred energy unit at the atomic and subatomic scale because it produces manageable numbers, whereas expressing the same energies in Joules yields extremely small values. Particle physicists use eV (and its multiples keV, MeV, GeV, TeV) to describe collision energies and particle masses. Semiconductor engineers express band gap energies in eV to characterize materials like silicon (1.12 eV) and gallium arsenide (1.42 eV). Spectroscopists convert photon energies between eV and Joules to relate quantum measurements to macroscopic physical quantities. Understanding this conversion connects the quantum world to the classical SI framework, enabling researchers to translate between the natural language of particle physics and the universal standards of measurement.

Conversion Formula

To convert electronvolts to Joules, multiply by 1.60218 × 10^-19. This factor is the elementary charge (the charge of a single electron) expressed in Coulombs. Since one electronvolt is defined as the energy gained by one electron charge moving through one volt of potential, and since energy equals charge times voltage (E = qV), the conversion factor is numerically equal to the electron charge: 1 eV = 1.602176634 × 10^-19 Joules (exact as of 2019 SI redefinition).

Step-by-Step Example

Understanding Electronvolts and Joules

What is a Electronvolt?

The electronvolt was introduced in the early 20th century as particle physics emerged as a discipline. As scientists began studying atomic spectra, radioactive decay, and particle interactions, they needed a convenient energy unit at the atomic scale. The eV was naturally defined by the experimental setup of accelerating charged particles through electric fields. It became standard in nuclear physics by the 1930s and has since been adopted across all branches of physics dealing with atomic and subatomic phenomena. The unit is accepted for use with the SI system despite not being a formal SI unit.

What is a Joule?

The Joule, the SI unit of energy, was named after James Prescott Joule and adopted in 1960 by the General Conference on Weights and Measures. It is defined as one kilogram times meter squared per second squared. In the 2019 SI redefinition, the Joule's value was further anchored by fixing the values of fundamental constants including the Planck constant and the elementary charge. This redefinition made the Joule-to-electronvolt conversion exact rather than approximate, strengthening the connection between macroscopic and quantum energy measurements.

Practical Applications

Particle physicists convert collision energies from eV to Joules when relating accelerator experiments to macroscopic energy scales. Semiconductor manufacturers convert band gap values from eV to Joules for thermodynamic calculations in device fabrication. X-ray crystallographers convert photon energies from eV to Joules to calculate wavelengths and frequencies. Nuclear physicists express binding energies per nucleon in eV and convert to Joules for mass-energy equivalence calculations. Solar cell researchers convert photon absorption energies from eV to Joules when computing theoretical efficiency limits.

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