Contour line#Temperature and related subjects

Isotherms (Greek ἴσος isos, equal to ' and θέρμη Therme, heat ') are lines of equal temperature:

They belong to the contour lines and are used in numerous charts from all areas of natural and engineering sciences.

Thermodynamics

In thermodynamics, the isotherms are shown for example, in the PV diagram to depict the relationship between pressure p and volume V at a constant temperature. If pressure and volume change while the temperature remains the same, there is an isothermal change of state. In the pV diagram corresponds to the work performed a cyclic process of the surface enclosing the process curves of the cycle. An example of a cyclic process represent two isotherms and two isochores dar.

The isotherm of an ideal gas in the PV diagram, derived from the thermal equation of state by a hyperbola writable.

Another example of isotherms in thermodynamics are sorption isotherms.

Meteorology

In meteorology isotherms are used to characterize the meteorological weather maps the areas of equal temperature. The spacing of the isotherms is an indication of the scale of the temperature gradient in an area. This can be derived from the arrangement of adjacent isotherms temperature gradient is an important element in the weather forecast.

Are usual Jahresisothermen that are created based on the annual average temperatures, as well as January and Juliisotherme.