Definition of an Electron Volt
An electron volt (eV) is a unit of energy equal to the kinetic energy gained by a single electron when it accelerates through an electric potential difference of one volt in a vacuum. It is a very small amount of energy, making it particularly convenient for calculations involving individual atoms, electrons, and photons.
Relationship to Charge and Potential
The value of an electron volt is derived from the elementary charge of an electron (approximately 1.602 × 10⁻¹⁹ Coulombs) multiplied by a potential difference of 1 Volt. This means 1 eV = 1.602 × 10⁻¹⁹ Joules. It directly connects the electrostatic potential and the kinetic energy of charged particles.
Practical Applications and Examples
Electron volts are routinely used to quantify the energy of photons in light (e.g., visible light photons have energies around 2-3 eV), the binding energies of electrons in atoms (ionization energies are often in eV), and the energies of particles in accelerators. For instance, the energy required to remove an electron from a hydrogen atom is about 13.6 eV.
Why Use Electron Volts?
Using electron volts simplifies calculations in atomic, nuclear, and particle physics by providing manageable numbers for extremely small energy values. Expressing these energies in Joules would result in cumbersome scientific notation with very small exponents, making eV a more intuitive and practical unit for these specific scientific domains.