24
3 System of Units
assumed to be independent of each other and that can be used, using the formulas,
to express the derived quantities of the system. Therefore, the derived quantity is
a quantity determined in a given system as a function of the basic quantity of the
system. From the above description, it can be seen that the appropriate system of
quantities is an important aspect in ordering the units of measurement.
Apart of the system of quantities, it is also necessary to establish a system of
units of measurement that is an ordered set of units of measurement of the base and
derived units related to a specific system of quantities.
The unit of measurement of a given quantity is determined in order to allow quantitative comparison of the various values of the same quantity. The symbol of a unit
of measurement is called a contractual symbol indicating the unit of measurement;
for example, m, a symbol for meter; kg, a symbol for kilogram; and s, a symbol for
second. Units of measurement, as well as physical quantities, are divided into the
base and derived units of measurement. The system of units thus consists of primary
units of measurement, assumed contractually, and the derived units built on them,
of a complex nature. Some derived units have names and symbols of their own; for
example, newton (N), volt (V).
The base unit of measurement is the unit of measurement of individual basic
quantities.
The derived unit of measurement is the unit of measurement of one of the
derived quantities.
Establishing the systems of units was preceded by establishing adequate reference
units of various quantities. These standards, taken from nature or assumed contractually, made it possible to take measurements (see Chap. 2). Through the combination
of the chosen units of other quantities as derivatives were formed. For each quantity,
any value can be basically assumed as its unit.
As already mentioned, the idea of the metric system, the system of units based
on the meter and kilogram, was created in France, when two platinum reference
standards artefacts for the meter and the kilogram were deposited in the French
Archives de la République in Paris in 1799. The metric system uses decimal multiples
and submultiples of units of measurement. Later on, the French Academy of Sciences
was obliged by the National Assembly to design a new system of units for the world to
use, and as a result, in 1946, the MKSA (meter, kilogram, second, ampere) system was
accepted by the countries of the Metre Convention. In 1954, the MKSA system was
extended to incorporate the inclusion of the kelvin and the candela, and the adopted
the name of the international system of units—SI. This system was established in
1960 by the 11th General Conference of Weights and Measures (CGPM).
Another system of units, ensuring their consistency with the base units of the
system, was the CGS (centimeter, gram, second) system. It was initiated by C.F.
Gauss, who proposed in 1832 the principle of the structure of the system of units,
consisting of choosing the base quantities and establishing their units, which are also
3 System of Units
assumed to be independent of each other and that can be used, using the formulas,
to express the derived quantities of the system. Therefore, the derived quantity is
a quantity determined in a given system as a function of the basic quantity of the
system. From the above description, it can be seen that the appropriate system of
quantities is an important aspect in ordering the units of measurement.
Apart of the system of quantities, it is also necessary to establish a system of
units of measurement that is an ordered set of units of measurement of the base and
derived units related to a specific system of quantities.
The unit of measurement of a given quantity is determined in order to allow quantitative comparison of the various values of the same quantity. The symbol of a unit
of measurement is called a contractual symbol indicating the unit of measurement;
for example, m, a symbol for meter; kg, a symbol for kilogram; and s, a symbol for
second. Units of measurement, as well as physical quantities, are divided into the
base and derived units of measurement. The system of units thus consists of primary
units of measurement, assumed contractually, and the derived units built on them,
of a complex nature. Some derived units have names and symbols of their own; for
example, newton (N), volt (V).
The base unit of measurement is the unit of measurement of individual basic
quantities.
The derived unit of measurement is the unit of measurement of one of the
derived quantities.
Establishing the systems of units was preceded by establishing adequate reference
units of various quantities. These standards, taken from nature or assumed contractually, made it possible to take measurements (see Chap. 2). Through the combination
of the chosen units of other quantities as derivatives were formed. For each quantity,
any value can be basically assumed as its unit.
As already mentioned, the idea of the metric system, the system of units based
on the meter and kilogram, was created in France, when two platinum reference
standards artefacts for the meter and the kilogram were deposited in the French
Archives de la République in Paris in 1799. The metric system uses decimal multiples
and submultiples of units of measurement. Later on, the French Academy of Sciences
was obliged by the National Assembly to design a new system of units for the world to
use, and as a result, in 1946, the MKSA (meter, kilogram, second, ampere) system was
accepted by the countries of the Metre Convention. In 1954, the MKSA system was
extended to incorporate the inclusion of the kelvin and the candela, and the adopted
the name of the international system of units—SI. This system was established in
1960 by the 11th General Conference of Weights and Measures (CGPM).
Another system of units, ensuring their consistency with the base units of the
system, was the CGS (centimeter, gram, second) system. It was initiated by C.F.
Gauss, who proposed in 1832 the principle of the structure of the system of units,
consisting of choosing the base quantities and establishing their units, which are also