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  2. Historical definitions of the SI base units - Wikipedia

    en.wikipedia.org/wiki/Historical_definitions_of...

    Previous (1967): ⁠ 1 / 273.16 ⁠ of the thermodynamic temperature of the triple point of water. Current (2019): The kelvin is defined by setting the fixed numerical value of the Boltzmann constant k to 1.380 649 × 10 −23 J⋅K −1, (J = kg⋅m 2 ⋅s −2), given the definition of the kilogram, the metre, and the second. mole

  3. Gram - Wikipedia

    en.wikipedia.org/wiki/Gram

    The gram (originally gramme; [1] SI unit symbol g) is a unit of mass in the International System of Units (SI) equal to one thousandth of a kilogram.. Originally defined as of 1795 as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre [1 cm 3], and at the temperature of melting ice", [2] the defining temperature (≈0 °C) was later changed to 4 ...

  4. Metric system - Wikipedia

    en.wikipedia.org/wiki/Metric_system

    The metric system is a decimal-based system of measurement. The current international standard for the metric system is the International System of Units (Système international d'unités or SI), in which all units can be expressed in terms of seven base units: the metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and ...

  5. Temperature - Wikipedia

    en.wikipedia.org/wiki/Temperature

    Empirically based temperature scales rely directly on measurements of simple macroscopic physical properties of materials. For example, the length of a column of mercury, confined in a glass-walled capillary tube, is dependent largely on temperature and is the basis of the very useful mercury-in-glass thermometer.

  6. Conversion of units - Wikipedia

    en.wikipedia.org/wiki/Conversion_of_units

    Last, multiply the original expression of the physical value by the fraction, called a conversion factor, to obtain the same physical value expressed in terms of a different unit. Note: since valid conversion factors are dimensionless and have a numerical value of one , multiplying any physical quantity by such a conversion factor (which is 1 ...

  7. Table of specific heat capacities - Wikipedia

    en.wikipedia.org/wiki/Table_of_specific_heat...

    A Assuming an altitude of 194 metres above mean sea level (the worldwide median altitude of human habitation), an indoor temperature of 23 °C, a dewpoint of 9 °C (40.85% relative humidity), and 760 mmHg sea level–corrected barometric pressure (molar water vapor content = 1.16%). B Calculated values *Derived data by calculation.

  8. List of metric units - Wikipedia

    en.wikipedia.org/wiki/List_of_metric_units

    The centimetre–gram–second system of units (CGS) is based on three base units: centimetre, gram and second. Its subsystems (CGS-ESU, CGS-EMU and CGS-Gaussian) have different defining equations for their systems of quantities for defining electromagnetic quantities and hence the associated units, with CGS-Gaussian units being selected from each of the other two subsystems.

  9. Mechanical equivalent of heat - Wikipedia

    en.wikipedia.org/wiki/Mechanical_equivalent_of_heat

    Though a standardised value of 4.1860 J·cal −1 was established in the early 20th century, in the 1920s, it was ultimately realised that the constant is simply the specific heat of water, a quantity that varies with temperature between the values of 4.17 and 4.22 J·g −1 ·°C −1.