## What is International System of Unit?

The International System of Units (SI), commonly known as the metric system, is the international standard for measurement. It is referred to as SI.

It was adopted as a worldwide system of measurements in 1960 at the 11th General Conference on Weight and Measures in Paris.

The SI is made up of 7 base units that define the 22 derived units with special names and symbols.

**Other Definitions of International System of Units**

- The International System of Units (SI) is a scientific method of expressing the magnitudes or quantities of seven important natural phenomena.

## What is the importance of International System of Units?

- It provides the internationally agreed means by which we make such measurements.
- The principle behind the International System of Units is to provide the same values for measurements such as length, weight, and time no matter where in the world measurement is performed.
- It provides definitions of units of measurement that are widely accepted in science and technology.

## What do you mean by Base Units?

Students can define the base unit by one of the following three definitions:

- A base unit is a unit adapted for the measurement of a base quantity
- The units that describe base quantities are called base units.
- Base units are defined by a particular process of measuring a base quantity.

Each base quantity has its SI unit.

## Tabulate the Base Quantities with their SI units and symbols.

Quantity Name | Symbol | Base Unit | Unit Symbol |
---|---|---|---|

Length | l | meter | m |

Mass | m | kilogram | kg |

Time | t | second | s |

Electric Current | I | ampere | A |

Intensity of Light | L | candela | cd |

Temperature | T | kelvin | K |

Amount of a Substance | n | mole | mol |

## What are Derived Units?

Students can define the derived unit by one of the following three definitions:

- A derived unit is a unit adapted for the measurement of a derived quantity
- The units that describe derived quantities are called derived units.
- Derived units are defined by a particular process of measuring a derived quantity.

Derived units are defined in terms of base units and are obtained by multiplying or dividing one or more base units with each other.

## Tabulate the Derived Quantities with their SI units and symbols.

Quantity Name | Symbol | Derived Unit | Symbol |
---|---|---|---|

Speed | v | meter per second | ms^{-1} |

Acceleration | a | meter per second per second | ms^{-2} |

Volume | V | cubic meter | m^{3} |

Force | F | newton | N or Kg m s^{-2} |

Pressure | P | pascal | Pa or N m^{-2} |

Density | p | kilogram per cubic per meter | kg m^{-3} |

Charge | Q | coulomb | C or As |

## Quiz

- International System of Units is also known as
- SI
- Metric System
- Both of the above
- None of the above

- International System of Units was adopted as a worldwide system of measurements in
- 1958
- 1960
- 1962
- 1964

- 11th General Conference on Weight and Measures was held in
- France
- Germany
- Paris
- America

- The SI is made up of how many base units?
- 5
- 6
- 7
- 8

- The “meter” is the base unit of
- Temperature
- Length
- Time
- None of the above

- Pascal is the SI unit of
- Force
- Pressure
- Density
- Electric Current

- Newton is the SI unit of
- Force
- Pressure
- Density
- Electric Current

- Mole is the SI unit of
- Electric Current
- Intensity of Light
- Amount of a Substance
- Density

- Coulomb is the SI unit of
- Intensity of Light
- Amount of a Substance
- Density
- Charge

- Cubic Meter is the SI unit of
- Speed
- Acceleration
- Force
- Volume

## Quiz with Answers

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