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The Boltzmann constant (k B or k) is the proportionality factor that relates the average relative thermal energy of particles in a gas with the thermodynamic temperature of the gas. [2] It occurs in the definitions of the kelvin (K) and the gas constant , in Planck's law of black-body radiation and Boltzmann's entropy formula , and is used in ...
In mathematics and physics, the heat equation is a certain partial differential equation. Solutions of the heat equation are sometimes known as caloric functions . The theory of the heat equation was first developed by Joseph Fourier in 1822 for the purpose of modeling how a quantity such as heat diffuses through a given region.
kT (also written as k B T) is the product of the Boltzmann constant, k (or k B), and the temperature, T.This product is used in physics as a scale factor for energy values in molecular-scale systems (sometimes it is used as a unit of energy), as the rates and frequencies of many processes and phenomena depend not on their energy alone, but on the ratio of that energy and kT, that is, on E ...
Quantity (common name/s) (Common) symbol/s Defining equation SI unit Dimension Temperature gradient: No standard symbol K⋅m −1: ΘL −1: Thermal conduction rate, thermal current, thermal/heat flux, thermal power transfer
The above differential equation, when integrated for a homogeneous material of 1-D geometry between two endpoints at constant temperature, gives the heat flow rate as =, where Δ t {\displaystyle \Delta t} is the time interval during which the amount of heat Q {\displaystyle Q} flows through a cross-section of the material,
where c p is the specific heat capacity for a constant pressure and c v is the specific heat capacity for a constant volume. [9] It is common, especially in engineering applications, to represent the specific gas constant by the symbol R. In such cases, the universal gas constant is usually given a different symbol such as R to distinguish it ...
The Stefan–Boltzmann constant, σ, is derived from other known physical constants: = where k is the Boltzmann constant, the h is the Planck constant, and c is the speed of light in vacuum. [19] [4]: 388
Together, ρc p can be considered the volumetric heat capacity (J/(m 3 ·K)). As seen in the heat equation , [ 5 ] ∂ T ∂ t = α ∇ 2 T , {\displaystyle {\frac {\partial T}{\partial t}}=\alpha \nabla ^{2}T,} one way to view thermal diffusivity is as the ratio of the time derivative of temperature to its curvature , quantifying the rate at ...