About SI system
Table of Contents
Background
The International System of Units (SI) serves as the modern form of the metric system and provides a standardized framework for measurements worldwide. It’s primary purposes are:
Uniformity: SI ensures that measurements are consistent and comparable globally, facilitating international trade, science, technology, and communication.
Simplicity: The system is based on decimal units, making calculations easier and reducing conversion errors compared to non-metric systems.
Precision: SI provides a high degree of accuracy in measurement, crucial for scientific research and technological development.
Adaptability: It can accommodate new discoveries and technologies through the introduction of additional units or revisions as needed.
SI system base units
The SI system is the international system of units that defines standardized units for scientific measurements. The SI system is based on seven base units:
| Base quantity | Base unit | ||
|---|---|---|---|
| Name | Typical symbol | Name | Symbol |
| time | t | second | s |
| length | l , x , r , etc. | metre | m |
| mass | m | kilogram | kg |
| electric current | I, i | ampere | A |
| thermodynamic temperature | T | kelvin | K |
| amount of substance | n | mole | mol |
| luminous intensity | I ᵥ | candela | cd |
Table created using tablesgenerator.com
Orders of magnitude
An order of magnitude refers to the size of values and their relationship to each other. Generally, orders of magnitude are used to estimate numbers and calculate how many times a value is larger or smaller than a certain reference value. Orders of magnitude are typically based on powers of ten.
Example
The number 10,000 can be expressed as an order of magnitude of 10⁴ (the order of magnitude is 4).
The number 0.0001 can be expressed as an order of magnitude of 10⁻⁴ (the order of magnitude is -4).
Orders of magnitude are particularly useful when dealing with very large or very small numbers, such as in astronomy or microbiology, making it easier to read and compare numbers.
Presentation of results
Presenting results is important to ensure they are understandable and comparable. The following principles are often used in this context:
Significant figures: When presenting results, significant figures are considered, which indicate the precision of the measurement. For example, if a measurement result is 2.5 cm and the measurement has two significant figures, it would not make sense to present the result as more precise, such as 2.50 cm.
Scientific notation: Orders of magnitude and scientific notation (e.g., 1.23 × 10⁻³) are used when presenting large or small values in a compact form.
Use of units: All measurements should be presented in SI units to ensure they are internationally comparable and understandable. For instance, temperature may be expressed in kelvins (K), and distance in meters (m).
Example of scientific presentation
Temperature: 300 K (temperature is expressed in kelvins, which is recommended in scientific writing)
Mass measurement: 5.3 × 10⁻³ kg (scientific notation is used here to express the order of magnitude)
Results may also vary depending on the precision of measurements, so it is important to also present uncertainties, such as ± 0.01 kg.
