SI prefixes (International System of Units) are used to indicate too large and too small values of physical quantities. These prefixes are placed in front of the corresponding symbols of quantities in physics. Let's consider in the article commonly used consoles, their meanings and notation.
What are the prefixes of SI in physics?
In the SI system, the International Chamber of Weights and Measures introduced prefixes for the values of physical quantities, which are given in the table below.
These consoles are the most commonly used. There are others, with greater and lesser degrees. So, the smallest prefix is yokto (y) - 10-24 , and the largest - 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 turns out to be inconvenient to use them if expressed in basic SI units. For these cases, prefixes are used. For example, atmospheric pressure on the surface of our planet is approximately 100,000 Pa, more often this value is recorded in the form of 100 kPa (kilopascal) or in the form of 0.1 MPa (megapascal).
Rules for using consoles
The use of SI prefixes is subject to the following rules:
- You can’t put two consoles together, for example, 10 -9 m can not be written as 1 μm (micromillimeter), but it should be written as 1 nm (nanometer).
- If the physical quantity in its designation has a degree and a prefix, then first you need to take into account the prefix, for example, km 2 - square kilometer.
Frequently used prefixes for the corresponding physical quantities
Theoretically, all SI prefixes can be used with any physical quantities, but traditionally it has turned out that only some of them are used with certain quantities. Below are common physical quantities and prefixes that are often used with them.
- Weight. It is often expressed in milligrams, kilograms, micrograms. For large masses, units such as megagrams and gigrams are almost not used, instead they use tons, with which these consoles are already used, for example, megatons.
- Volume. Milliliter, microliter, cubic kilometer, cubic decimeter are the main prefixes for this value.
- Length. For its measurement, kilometers, decimeters, centimeters, millimeters and smaller units are used. As in the case of volume, megameters and gigameters are not used. For large distances, astronomical values are used, for example, parsec.
- Time. Milliseconds, microseconds, and smaller consoles are often used to indicate time. Long time intervals are measured in hours and earth years, and units of a megasecond and a gigase second are used extremely rarely.