Fourier's law

Fourier's law states that heat flux is proportional to the negative temperature gradient, with thermal conductivity as the proportionality factor. It describes conductive heat transfer from warmer regions toward cooler ones.

Heat flux: Heat transfer per unit area and time, expressed as a vector describing the direction and rate of energy flow. Fourier's law relates this vector directly to the local temperature gradient.
Temperature: A physical quantity that characterizes thermal state and determines the direction of spontaneous heat transfer. Fourier's law uses spatial changes in temperature to determine conductive flow.
Thermal resistance: A measure of how strongly a component opposes heat flow, relating temperature difference to heat-transfer rate. Fourier's law gives the material and geometric basis for conduction resistance.
Newton's law of cooling: A model in which an object's heat-loss rate is proportional to its temperature difference from surrounding fluid. It describes convective exchange at a surface, whereas Fourier's law describes conduction within matter.
Temperature gradient: The spatial rate and direction of change in temperature. Its negative direction determines the direction of conductive heat flux.
Heat transfer: The movement of thermal energy between regions or bodies because of temperature differences. Fourier's law describes its conductive mode, rather than convection or radiation.
Thermal insulation: Materials and design strategies that reduce heat transfer between regions at different temperatures. Low conductivity limits the heat flux predicted by Fourier's law.
Stefan–Boltzmann law: A law stating that thermal radiation emitted by a blackbody scales with the fourth power of absolute temperature. It governs radiative transfer, which does not require the conductive temperature-gradient relation.
Thermal conductivity: A material property measuring its ability to conduct heat, usually expressed in watts per meter-kelvin. It sets the proportionality between temperature gradient and heat flux.
Thermodynamic equilibrium: A state in which macroscopic thermal and other thermodynamic variables do not change with time. A temperature gradient marks departure from uniform thermal equilibrium and drives conduction.

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