Systems of Units: SI and English Systems

• Systems of units are sets of standard measures to calculate lengths, mass, time, force, etc.
• They consist of basic and derived units created to improve understanding of the measurement process.
• The most common systems are the International System of Units (SI) and the English System.

International System of Units (SI)

• These units are the international measurement reference used by most people globally.
• Its function is to establish basic rules on measuring to have the same references everywhere.
• For distance or length, the meter (m) is used.
• Time is measured in seconds (s).
• Mass is measured in kilograms (kg).
• Electric current is measured in amperes (A).
• Temperature is measured in kelvin (K).
• The amount of substance is measured in mol (mol).
• Luminous intensity is measured in candelas (cd).

English or Anglo-Saxon System

• The English system is a set of non-metric units used mainly in the USA and parts of the UK.
• It is based on the inch, foot, yard, and mile.
• These units are being replaced by the International System of Units.

Origins

• The earliest systems of units emerged in France in the 18th century.
• This was due to the need to measure elements with the same pattern.
• Over time, it has become a tool for scientists, engineers, and other professionals.
• The SI, or International System of Units, was created in 1960.
• This took place at the eleventh General Conference on Weights and Measures in Paris, France.
• Six basic physical units were recognized: length, time, mass, electric current, temperature, and amount of substance, except the mole.
• The mole was added in 1971.