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To indicate weights and measures of substances, we utilise numbers and units. A number alone is insufficient to convey the amount of material or the length of given objects. Units must accompany numbers. A unit is a standard for measuring a quantity of the same kind. They are derived units and prefixes as well. The C.G.S. system and the S.I. system are two popular unit systems. The S.I. system is used in scientific and technical fields. Let us learn about units of measurement and their systems.
Measuring Units
A unit of measurement is a defined magnitude or measure of a certain quantity used as a benchmark for measuring other quantities of the same type. The legal agreement aids in the formation of numerous physical units. Any other quantity of that type could be expressed as a multiple of a measuring unit.
Physical quantiles are, for example, the lengths of specified objects. A metre is a measurement unit that represents a specified length.
Measurement determines how little or large a physical quantity is by comparing it to fundamental standard reference quantities of the same kind. It’s difficult to convey a physical quantity using only a number and no unit, leading to ambiguity and confusion.
For example, we need to calculate the shortest route between two cities, and the distance through route X is 300 metres, and through route Y is 3 km. Even though the number 3 is smaller than 300, route X with 300 metres is the shortest due to the unit. In this way, units are significant and convey meanings.
Hence, to avoid ambiguity and confusion of such kinds, the utilisation of units is quite helpful. A unit also has dimensions and dimensional formulas.
A dimension is a mathematical expression that expresses physical quantity in a certain direction. In mathematics, it is a line segment with a direction. Multiple units of base quantities are raised to power for getting dimensions for a physical amount.
System of Units
Units could be primary units as well as derived units and prefixes. Prefixes include centi, milli, micro, etc. There are various systems of units:
- The International System of Units, that is, the S.I. system
- The F.P.S. system of units
- The M.K.S system of units
- The C.G.S. system of units
The SI System of Units
The International System of units is the most popular system for weights and measures and is mainly used in scientific and technical fields.
There are seven base units in the S.I. system of units. The seven basic units are as follows:
- Second, which is the unit of time, is denoted by the symbol s
- Metre, which is the unit of length, is denoted by the symbol m
- Kilogram, which is the unit of mass, is denoted by the symbol kg
- Ampere, the unit of electric current, is denoted by the symbol A
- Kelvin is the unit of temperature denoted by the symbol K
- A mole is the unit of the amount of substance indicated by the symbol mol
- Candela is the unit of luminous intensity with the symbol cd
The most basic units of the S.I. system are length, mass, and time, that is, metre, kilogram, and second, respectively.
The inconsistency between the system of electromagnetic units and electrostatic units in the C.G.S. system was the main motive behind developing the S.I. system of units.
The above-stated units are the S.I. base units. Many derived units and prefixes are based on the base units.
The dimensional formula of derived units involves the base units.
C.G.S. System of Units
The centre-gram-second system of units is called the C.G.S. system of units.
The unit for measuring length in the C.G.S. system is a centimetre, the unit of mass is the gram. However, the unit of time is the same as the S.I. system, that is, second. The units of work and force in the C.G.S. system are erg and dyne.
The calculation made with the C.G.S. units is simple as constant coefficients are absent in the formulas of the relation between the quantities.
However, it is difficult to obtain the definition of the C.G.S. units by experiment.
In this system of units, the unit for the magnetic field and the units for the electric field are the same. The C.G.S. system of units is heavily based on the MKS system of units, that is, metre, kilogram, and second.
F.P.S. and MKS System of Units
F.P.S is the foot, pound, and second system of units where the foot is for length, the pound is for mass, and the second is the standard of time. The F.P.S system is used by the United States, Myanmar, and Liberia as the official metric system.
The MKS system uses metres, kilogram, and second for length, mass, and time. The base of the international system of units is laid by the MKS system. MKS units are generally used in engineering and physics.
