Kilojoule to Electron Volt
kJ
eV
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
| No conversion history to show. | ||
Quick Reference Table (Kilojoule to Electron Volt)
| Kilojoule (kJ) | Electron Volt (eV) |
|---|---|
| 1 | 6,241,509,074,460,762,607,776.24098093044589988697 |
| 4.184 | 26,114,473,967,543,830,750,935.79226421298564512707 |
| 8.368 | 52,228,947,935,087,661,501,871.58452842597129025413 |
| 100 | 624,150,907,446,076,260,777,624.09809304458998869659 |
| 500 | 3,120,754,537,230,381,303,888,120.49046522294994348295 |
| 1,000 | 6,241,509,074,460,762,607,776,240.9809304458998869659 |
| 8,400 | 52,428,676,225,470,405,905,320,424.23981574555905051353 |
About Kilojoule (kJ)
A kilojoule (kJ) equals 1,000 joules and is one of the most practical SI energy units for everyday human-scale work. Food energy is commonly labelled in kilojoules in Australia, the EU, and many other countries — the same information that the US labels in Calories. Physical exercise and metabolic rates are often quoted in kilojoules per hour. One kilojoule is roughly the energy released by a small firecracker, or the kinetic energy of a tennis ball traveling at 160 km/h.
A 100 mL glass of orange juice contains about 180 kJ of food energy. Running 1 km burns approximately 200–300 kJ depending on body weight.
About Electron Volt (eV)
An electron volt (eV) is the kinetic energy gained by a single electron accelerating through an electric potential difference of one volt — equal to approximately 1.602 × 10⁻¹⁹ joules. It is the natural energy unit of particle physics, atomic physics, and chemistry, where joules would yield unwieldy powers of 10. Photon energies, ionisation energies, bandgaps in semiconductors, and masses of subatomic particles (via E = mc²) are all expressed in eV, keV, MeV, or GeV.
Visible light photons carry 1.8–3.1 eV of energy. The proton rest mass is 938 MeV. The Large Hadron Collider accelerates protons to 6.5 TeV (6.5 × 10¹² eV).
Kilojoule – Frequently Asked Questions
Why do Australian food labels show kilojoules instead of calories?
Australia, New Zealand, and the EU mandate SI-based labeling, so food packages list energy in kilojoules. The US and Canada stuck with kilocalories (branded as "Calories"). To convert, divide kJ by 4.184 — a 500 kJ snack bar is about 120 kcal. Most Australian shoppers learn the kJ scale by familiarity rather than converting every time.
How many kilojoules does a person burn walking for 30 minutes?
A 70 kg person walking briskly at 5.5 km/h burns roughly 600–700 kJ in 30 minutes (about 150–170 kcal). That is roughly one banana or a small flat white. Running the same distance roughly triples the kilojoule burn because the body must lift itself off the ground with every stride.
What is the difference between kJ and kcal on a food label?
They measure the same thing — food energy — in different units. One kilocalorie (kcal) equals 4.184 kilojoules (kJ). European and Australian labels show both; US labels show only kcal (labelled "Calories"). A 2,000 kcal/day diet is 8,368 kJ/day. Nutritionists consider the two interchangeable for dietary guidance.
How much energy in kilojoules does a smartphone battery hold?
A typical smartphone battery rated at 15 Wh holds about 54 kJ. That is roughly the food energy in a single sugar cube (17 kJ per cube times three). A laptop battery at 60 Wh stores about 216 kJ, and a Tesla Model 3 battery pack at 60 kWh stores 216,000 kJ — enough dietary energy to feed a person for about 25 days.
Is a kilojoule a large or small amount of energy?
It is a middle-ground unit — too large for electronics (which use millijoules) and too small for household energy bills (which use megajoules or kWh). One kilojoule is the kinetic energy of a tennis ball served at about 160 km/h, the energy in a small sip of juice, or the heat generated by a 100 W bulb in ten seconds. It sits at the human snack-and-exercise scale.
Electron Volt – Frequently Asked Questions
Why do particle physicists use electron volts instead of joules?
Because subatomic energies in joules have absurdly small exponents — a visible-light photon carries about 3 × 10⁻¹⁹ J, but a convenient 1.9 eV. The electron volt is scaled to the quantum world, making numbers human-readable. It also doubles as a mass unit (via E = mc²): a proton is 938.3 MeV/c², far easier to work with than 1.673 × 10⁻²⁷ kg.
How much energy in electron volts does visible light carry?
Visible light photons range from about 1.65 eV (deep red, 750 nm) to 3.1 eV (violet, 400 nm). Green light, where the human eye is most sensitive, sits around 2.3 eV. Ultraviolet photons start at 3.1 eV and can exceed 100 eV in the extreme UV. These energies are why UV can damage DNA (breaking molecular bonds of 3–5 eV) while visible light cannot.
What is the relationship between electron volts and semiconductor bandgaps?
A semiconductor's bandgap — the minimum energy to free an electron from its bond — is expressed in eV. Silicon has a bandgap of 1.12 eV, gallium arsenide 1.42 eV, and gallium nitride 3.4 eV. The bandgap determines which wavelengths of light a solar cell can absorb and what color an LED emits. Lower bandgap means longer-wavelength (redder) light.
How many electron volts does the Large Hadron Collider produce?
The LHC accelerates protons to 6.5 TeV (6.5 × 10¹² eV) per beam, giving collisions a center-of-mass energy of 13 TeV. That sounds enormous, but 13 TeV is only about 2 microjoules — the kinetic energy of a flying mosquito. The power of the LHC lies in concentrating that energy into a space a million times smaller than an atom.
How do you convert electron volts to joules?
Multiply by 1.602 176 634 × 10⁻¹⁹. So 1 eV = 1.602 × 10⁻¹⁹ J, 1 keV = 1.602 × 10⁻¹⁶ J, and 1 MeV = 1.602 × 10⁻¹³ J. This conversion factor is exactly the elementary charge in coulombs, because an electron volt is defined as the energy gained by one electron charge crossing one volt of potential.