What SI prefixes exist and how they are used

2024 Author: Angel Austin | [email protected]. Last modified: 2023-12-17 05:14

SI prefixes (International System of Units) are used to designate too large and too small values of physical quantities. These prefixes are placed before the corresponding symbols of quantities in physics. Consider in the article frequently used prefixes, their meanings and designations.

What are the SI prefixes in physics?

In the SI system, the International Chamber of Weights and Measures introduced prefixes for the values of physical quantities, which are shown in the table below.

These prefixes are the most commonly used. There are others - with greater and lesser degrees. So, the smallest prefix is yocto (y) - 10^-24, and the largest is iota (Y) - 10^24.

Thus, SI prefixes cover values from 10^-24 to 10^{24. Since quantities in physics can have both large and small values, it is inconvenient to use them if they are expressed in basic SI units. For these cases, prefixes are used. For example, atmospheric pressure on the surface of our planetis approximately 100,000 Pa, more often this value is written as 100 kPa (kilopascal) or as 0.1 MPa (megapascal).}

Using prefixes

The use of SI prefixes is subject to the following rules:

1. You cannot put two prefixes together, for example, 10-9 m cannot be written as 1 µm (micromillimeter), but should be written as 1 nm (nanometer).
2. If a physical quantity in its designation has a degree and a prefix, then you first need to take into account the prefix, for example km2 - square kilometer.

Frequently used prefixes for corresponding physical quantities

Theoretically, all SI prefixes can be used with any physical quantities, but traditionally, only some of them are used with certain quantities. The following are common physical quantities and prefixes that are often used with them.

• Mass. It is often expressed in milligrams, kilograms, micrograms. For large masses, units such as megagrams and gigagrams are almost never used, instead of them they use tons, with which these prefixes are already used, for example, megaton.
• Volume. Milliliter, microliter, cubic kilometer, cubic decimeter are the main prefixes for this value.
• Length. To measure it, kilometers, decimeters, centimeters, millimeters and smaller units are used. As with volume, megameters and gigameters are not used. For long distances useastronomical quantities, such as parsec.
• Time. Millisecond, microsecond and smaller prefixes are often used to denote time. Large intervals of time are measured in hours and Earth years, while the units of megasecond and gigasecond are rarely used.