What is electronvolt?
An electronvolt is a unit of energy equal to the work done on an electron by a potential difference of one volt, approximately 1.602 × 10⁻¹⁹ joules. It is used in atomic physics, particle physics, and quantum mechanics.
Real-world uses
The electronvolt is the standard energy unit in particle physics, atomic physics, and semiconductor science. X-ray photon energies are measured in keV; visible light photons in eV (about 1.8–3.1 eV); nuclear reactions in MeV; and particle accelerator energies in GeV or TeV.
History
The electronvolt came into use in the early 20th century with the development of quantum mechanics and experimental atomic physics. As physicists began measuring energies of electrons and photons, the eV provided a convenient unit far smaller than the joule but appropriate for subatomic-scale phenomena.
Common mistakes
Confusing the electronvolt with a unit of voltage—it is a unit of energy equal to the kinetic energy gained by one electron accelerated through a potential difference of one volt (1 eV = 1.602 × 10⁻¹⁹ J). Also mixing up the scale prefixes (keV, MeV, GeV, TeV) when discussing different physical phenomena.
What is watt hour?
A watt hour is a unit of energy equal to the power of one watt sustained for one hour. It is used to measure small amounts of electrical energy consumption, particularly in battery capacities and portable electronics.
Real-world uses
Watt-hours measure the energy stored in or consumed from batteries, small electronics, and portable power stations. A smartphone battery holds roughly 10–15 Wh; a laptop battery 40–100 Wh. Solar panel output for small installations is often quoted in Wh per day.
History
The watt-hour emerged as a practical energy unit in the late 19th century with the commercialisation of electric power distribution. It offered a convenient scale between the joule (too small) and kilowatt-hour (too large) for everyday portable energy applications.
Common mistakes
Confusing watt-hours (energy) with watts (power). A device rated at 5 W running for 3 hours consumes 15 Wh. Also, treating Wh and mAh as interchangeable without knowing voltage: Wh = mAh × V ÷ 1000.
When is this conversion used?
Converting electronvolt to watt hour is useful in the energy domain when comparing values across different measurement standards or applying formulas that require a specific unit.
Worked examples
1 electronvolt = 4.450491e-23 watt hour
1 watt hour = 3,600 joule
How to convert electronvolt to watt hour
To convert electronvolt to watt hour, multiply the value by 4.450491e-23.
To convert watt hour back to electronvolt, multiply by 2.246943e+22.
Measurement standards
The joule is the SI derived unit of energy, defined as one kilogram-metre-squared per second-squared (kg·m²/s²). The kilowatt-hour, equal to exactly 3.6 megajoules, is accepted for use with the SI by the BIPM for practical electricity metering.
Did you know?
A single bolt of lightning releases roughly 1 to 5 gigajoules of energy, yet only a small fraction reaches the ground as electrical current. Most of the energy dissipates as light, heat, and the thunder shockwave.
Quick reference: electronvolt to watt hour
| electronvolt | watt hour |
|---|---|
| 0.1 | 4.450491e-24 |
| 0.5 | 2.225245e-23 |
| 1 | 4.450491e-23 |
| 2 | 8.900981e-23 |
| 5 | 2.225245e-22 |
| 10 | 4.450491e-22 |
| 25 | 1.112623e-21 |
| 50 | 2.225245e-21 |
| 100 | 4.450491e-21 |
| 250 | 1.112623e-20 |
| 500 | 2.225245e-20 |
| 1,000 | 4.450491e-20 |
Common values
| electronvolt | watt hour | |
|---|---|---|
| A food calorie (1 kcal) | 2.611447e+22 electronvolt | 1.16222222 watt hour |
| A AA battery | 5.842052e+22 electronvolt | 2.6 watt hour |
| Boiling a kettle | 2.621434e+24 electronvolt | 116.66666667 watt hour |
| Daily human diet (2000 kcal) | 5.222895e+25 electronvolt | 2,324.44444444 watt hour |
| 1 gallon of gasoline | 8.223812e+26 electronvolt | 36,600 watt hour |
Available Energy units
More electronvolt conversions
- Convert electronvolt to joule
- Convert electronvolt to kilojoule
- Convert electronvolt to kilowatt hour
- Convert electronvolt to calorie (thermochemical)
- Convert electronvolt to kilocalorie (dietary)
- Convert electronvolt to watt hour
- Convert electronvolt to megajoule
- Convert electronvolt to British thermal unit
- Convert electronvolt to therm (US)
Assumption: calorie means thermochemical calorie, and therm means US therm.