It is crucial to understand that electron-volts (eV) and volts (V) are units measuring different physical quantities. An electron-volt is a unit of energy, while a volt is a unit of electric potential or voltage. Therefore, you cannot directly "change" or convert electron-volts into volts in the same way you might convert meters to feet. They describe distinct aspects of an electrical or physical system.
The Definition and Relationship of Electron-Volt to Volt
The electron-volt (eV) is specifically defined based on the volt (V) and the elementary charge.
- Electron-Volt (eV): One electron-volt is defined as the amount of kinetic energy gained by a single elementary charge (like an electron or proton) when it is accelerated through an electric potential difference of one volt in a vacuum.
- Volt (V): One volt is defined as the electric potential difference between two points that will impart one joule of energy per coulomb of charge passing through it.
The fundamental relationship between energy (E), charge (q), and potential difference (V) is:
Energy (E) = Charge (q) × Potential Difference (V)
Given that the elementary charge, denoted as e, is approximately 1.602176634 × 10⁻¹⁹ Coulombs (C):
- When an electron (with charge e) moves through a potential difference of 1 Volt, it gains 1 electron-volt of energy.
- This directly means: 1 eV = e × 1 V.
- Since 1 Joule (J) is defined as 1 Coulomb (C) multiplied by 1 Volt (V) (1 J = 1 C ⋅ 1 V), then substituting the value of e:
1 eV = 1.602176634 × 10⁻¹⁹ Joules (J).
Numerical Equivalence for Electron Energy
While eV and V are different units, a common point of understanding arises when discussing the energy of an electron. Because the electron-volt is defined using the elementary charge and the volt, there's a direct numerical equivalence:
If a single electron gains an energy of 'X' electron-volts, it means it was accelerated through an electric potential difference of 'X' volts.
This numerical equivalence makes it appear, in certain contexts, as if eV and V are interchangeable, but it's crucial to remember their distinct physical meanings.
Here's a table illustrating this numerical equivalence for an electron:
| Energy Gained by an Electron (eV) | Equivalent Potential Difference (V) |
|---|---|
| 1 eV | 1 V |
| 10 eV | 10 V |
| 100 eV | 100 V |
| 5000 eV | 5000 V |
| 1 MeV (10⁶ eV) | 1 MV (10⁶ V) |
Understanding a Specific Numerical Relation
In some contexts, when discussing the relationship between electron-volts and volts, you might encounter a numerical value, such as 1.602176634 x 10^-19. For instance, you might see a statement suggesting to consider multiplying the number of electron-volts by the conversion factor related to 1 eV = 1.602176634 x 10^-19 V.
It is critical to understand that this numerical value (1.602176634 x 10^-19) precisely represents the elementary charge (e) in Coulombs (C). It is not a direct unit conversion factor that transforms an energy unit (eV) into a potential unit (V). Instead, this value is fundamental to the definition of the electron-volt itself, linking energy in Joules to potential in Volts through the elementary charge.
Practical Contexts
- Electron-volts (eV) are commonly used in fields like particle physics, nuclear physics, and solid-state physics to describe the energy of particles or energy levels within atoms and materials, as these energies are typically very small when expressed in Joules.
- Volts (V) are universally used in electrical engineering and everyday applications to describe electric potential difference, often referred to as voltage.
