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 therm (US)?

A US therm is a unit of energy equal to 100,000 BTU. It is used by gas utility companies in the United States as the standard billing unit for natural gas consumption.

Real-world uses

The therm is used in the United States and United Kingdom for natural gas billing. One therm equals 100,000 BTU (approximately 29.3 kWh). Residential gas bills in the US often list consumption in therms. It is also used in industrial gas metering and procurement contracts.

History

The therm was introduced as a practical unit for natural gas billing in the early 20th century, when gas supply companies needed a convenient large-scale energy unit for residential and commercial customers. It consolidated prior inconsistent measurement practices in the gas industry.

Common mistakes

Confusing the therm with the BTU—1 therm = 100,000 BTU. Also, the US therm and the UK therm differ slightly (the UK therm is based on 105.5 MJ, while the US therm is exactly 100,000 BTU ≈ 105.48 MJ). Not to be confused with the thermie (a metric unit of heat).

When is this conversion used?

Converting electronvolt to therm (US) 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 = 1.518564e-27 therm (US)

1 therm (US) = 105,506,000 joule

How to convert electronvolt to therm (US)

To convert electronvolt to therm (US), multiply the value by 1.518564e-27.

To convert therm (US) back to electronvolt, multiply by 6.585167e+26.

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 therm (US)

electronvolt	therm (US)
0.1	1.518564e-28
0.5	7.592822e-28
1	1.518564e-27
2	3.037129e-27
5	7.592822e-27
10	1.518564e-26
25	3.796411e-26
50	7.592822e-26
100	1.518564e-25
250	3.796411e-25
500	7.592822e-25
1,000	1.518564e-24

Common values

	electronvolt	therm (US)
A food calorie (1 kcal)	2.611447e+22 electronvolt	0.00003966 therm (US)
A AA battery	5.842052e+22 electronvolt	0.00008872 therm (US)
Boiling a kettle	2.621434e+24 electronvolt	0.00398082 therm (US)
Daily human diet (2000 kcal)	5.222895e+25 electronvolt	0.07931302 therm (US)
1 gallon of gasoline	8.223812e+26 electronvolt	1.24883893 therm (US)

Available Energy units

More electronvolt conversions

Assumption: calorie means thermochemical calorie, and therm means US therm.