Scientific

Boltzmann Constant

Definition

A fundamental physical constant with the exact value 1.380649 × 10⁻²³ J/K, relating the average thermal kinetic energy of particles to the absolute temperature.

Explanation

The average kinetic energy of a gas molecule is (3/2)k₂T: at room temperature (293 K), this is 6.07 × 10⁻²¹ J = 0.038 eV per molecule. Since 2019, the kelvin is defined by fixing k₂ to exactly 1.380649 × 10⁻²³ J/K. The Boltzmann constant also appears in entropy (S = k₂ ln W) and the ideal gas law, connecting thermodynamics to statistical mechanics.

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