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  2. SI base unit - Wikipedia

    en.wikipedia.org/wiki/SI_base_unit

    "The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10 −34 when expressed in the unit J s, which is equal to kg m 2 s −1, where the metre and the second are defined in terms of c and ∆ν Cs." [1] The mass of one litre of water at the temperature ...

  3. Energy conversion efficiency - Wikipedia

    en.wikipedia.org/wiki/Energy_conversion_efficiency

    The electrical energy input of this cell is 1.20 times greater than the theoretical minimum so the energy efficiency is 0.83 compared to the ideal cell. A water electrolysis unit operating with a higher voltage that 1.48 V and at a temperature of 25 °C would have to have heat energy removed in order to maintain a constant temperature and the ...

  4. Specific energy - Wikipedia

    en.wikipedia.org/wiki/Specific_energy

    Specific energy has the same units as specific strength, which is related to the maximum specific energy of rotation an object can have without flying apart due to centrifugal force. The concept of specific energy is related to but distinct from the notion of molar energy in chemistry , that is energy per mole of a substance, which uses units ...

  5. Specific heat capacity - Wikipedia

    en.wikipedia.org/wiki/Specific_heat_capacity

    Sometimes the gram is used instead of kilogram for the unit of mass: 1 J⋅g −1 ⋅K −1 = 1000 J⋅kg −1 ⋅K −1. The specific heat capacity of a substance (per unit of mass) has dimension L 2 ⋅Θ −1 ⋅T −2, or (L/T) 2 /Θ. Therefore, the SI unit J⋅kg −1 ⋅K −1 is equivalent to metre squared per second squared per kelvin ...

  6. Historical definitions of the SI base units - Wikipedia

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

    Giorgi later identified the need for an electrical base unit, for which the unit of electric current was chosen for SI. Another three base units (for temperature, amount of substance, and luminous intensity) were added later. [1] The early metric systems defined a unit of weight as a base unit, while the SI defines an analogous unit of mass.

  7. Heat capacity - Wikipedia

    en.wikipedia.org/wiki/Heat_capacity

    The SI unit of heat capacity is joule per kelvin (J/K). Heat capacity is an extensive property. The corresponding intensive property is the specific heat capacity, found by dividing the heat capacity of an object by its mass. Dividing the heat capacity by the amount of substance in moles yields its molar heat capacity.

  8. Energy density - Wikipedia

    en.wikipedia.org/wiki/Energy_density

    But as a source of heat or for use in a heat engine, the relevant quantity is the change in standard enthalpy or the heat of combustion. There are two kinds of heat of combustion: The higher value (HHV), or gross heat of combustion, includes all the heat released as the products cool to room temperature and whatever water vapor is present ...

  9. Units of energy - Wikipedia

    en.wikipedia.org/wiki/Units_of_energy

    Because of the relativistic equivalence between mass and energy, the eV is also sometimes used as a unit of mass. The Hartree (the atomic unit of energy) is commonly used in the field of computational chemistry since such units arise directly from the calculation algorithms without any need for conversion. Historically Rydberg units have been used.