The joule is the SI unit of energy, work and heat. Defined as one newton-metre or one watt-second. Named after James Prescott Joule who demonstrated the mechanical equivalent of heat. Lifting a 100 g apple 1 metre requires about 1 J.
Real-world: Lifting a 100 g apple 1 m: ≈ 1 J. 100 kcal snack: 418,400 J. Hand grenade: ~650 kJ.
Read full joule reference →The electronvolt equals 1.602 × 10⁻¹⁹ joules — the energy gained by an electron accelerated through 1 volt. It is the natural energy unit of atomic, nuclear and particle physics. Chemical bonds are a few eV; LHC protons reach 7 TeV = 7 × 10¹² eV.
Real-world: Silicon band gap: 1.12 eV. Hydrogen ionization: 13.6 eV. LHC proton: 7 TeV. Photon wavelength 500 nm = 2.5 eV.
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