Si Units List - Definition, Advantages, FAQs
The SI unit refers to the International System of Units. It is a system of measuring things applied everywhere in the world. Scientists and engineers apply it so measurements are universal. The SI system consists of seven base units, such as metre for measuring length, kilogram for weight, and second for time. We can derive other units such as newton for force and joule for work from these. SI units can also be expressed in larger or smaller multiples through prefixes such as kilo (1000 times) or milli (1/1000). These are powers of 10. It makes it easy and right for everyone to measure, compare, and interpret results in science and everyday life.
This Story also Contains
- What is Unit?
- What is SI Unit ?
- Seven Fundamental SI Units
- Define Derived Units
- Advantages of SI units:
Also read -
What is Unit?
The term unit indicates the amount or magnitude of any quantity which is measurable. Different units are used to indicate different measurements of particular kind of quantities.
What is unit in Physics?
In physics, there are a lot of physical quantities which are measured to perform an experiment and a lot of physical quantities which form the basis of mathematical equations which govern laws of physics such as length, mass and many more. In order to measure such physical quantities, Appropriate units are made to measure them accurately.
What is SI Unit ?
An SI unit is the standard unit of a physical quantity accepted internationally for scientific and technical measurements.
Seven Fundamental SI Units
In physics, there are seven fundamental physical quantities which form the basis for deriving any other physical quantities. These seven fundamental physical quantities are listed as:
| Physical Quantity | SI Unit | Symbol |
| Length | metre | m |
| Mass | kilogram | kg |
| Time | second | s |
| Electric current | ampere | A |
| Temperature | kelvin | K |
| Amount of substance | mole | mol |
| Luminous intensity | candela | cd |
Define Derived Units
In physics, other than these seven fundamental physical quantities, any physical quantity can be derived from the relationship between these fundamental physical quantities and hence, these quantities are called derived quantities, and units of such quantities are known as derived units.
Some of the most common and used derived units are listed below with their definition, SI units, and their symbols.
|
Quantity Name
|
Definition
|
SI unit
|
symbol
|
|
Area
| It’s the amount of space covered by an object in two-dimensional plane | meter square | m2 |
| Volume | It’s the amount of space covered by an object in three-dimensional space. | meter cube | m3 |
| Velocity | Velocity is the ratio of distance covered by a body over time. | meter per second | ms-1 |
| Acceleration | Acceleration is the ratio of the velocity of a body over time. | meter per second square | ms-2 |
| Force | The product between mass of a body and the acceleration produced in it is called Force. | Newton | N |
| Frequency | The number of oscillations of a body in one second is called frequency. | Hertz | Hz |
| Work | The product of force applied on a body and the displacement covered by it is known as work done. | Joule | J |
| Pressure | Pressure is the ratio between force acting on a body to the area to which force is applied. | Pascal | Pa |
| Power | Power is defined as the ratio of work done by a body over a given period of time. | Watts | W |
| Density | Density is defined as the ratio between mass and volume of a body. | Kilogram per meter cube | Kgm-3 |
These are some derived units and there are more, in brief other than those seven fundamental physical quantities every quantity that is measurable in physics will be derived from those seven fundamental physical quantities and their SI unit name and symbol is after the scientist who discovered a particular kind of physical quantity. For example, It was. Isaac Newton gave the idea of force so, the SI unit of force or derived unit of force is called Newton, named after S. Isaac Newton.
Advantages of SI units:
- From country to country, we don’t need to convert one unit of any physical quantity measured to another system of units, SI units provide standard units used by all countries in the scientific field. This is the most important advantage of using SI units.
- Some physical quantities have very long expressions for their measurements of units, SI units provide special memorable symbols for each fundamental physical quantity SI units which are easy to represent the unit of measurement of any physical quantity.
- The fundamental physical quantities are used to determine units of measurements of other physical quantities known as derived units so, the SI unit of fundamental physical quantities gives the advantage to derive any physical quantity SI unit.
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Frequently Asked Questions (FAQs)
In physics, there are seven fundamental physical quantities which are the basis in SI units system to derive any desired physical quantity. These seven fundamental physical quantities are listed below along with their SI units and symbols.
Length. SI unit of length is called a metre having symbol as m.
Time. SI unit of time is called the second having a symbol as s.
Mass. SI unit of mass is kilogram having symbol as kg.
Electric current. SI unit of electric current is called an ampere symbol as A.
Luminous Intensity. SI unit of luminous intensity is called candela having the symbol as Cd.
Amount of substance. SI unit of amount of substance is called mole having symbol as mol.
Temperature. SI unit of temperature is called kelvin having the symbol as K.
The SI unit of time is known as seconds and the symbol is denoted as s. It is one of the fundamental physical quantities which is listed in SI units of measurement.
There are seven fundamental physical quantities namely Length, Mass, Time, Luminous Intensity, Electric current, Amount of substance, Temperature. Other than these seven fundamental physical quantities listed by International system of units, all the physical quantities SI units can be derived from these seven units such as Area, Volume, Frequency and many more useful physical quantities, these are all derived from seven fundamental physical quantities hence known as derived units.
According to International system of units, seven fundamental units are Length(metre), Time (seconds), Temperature (Kelvin), Luminous Intensity (Candela), Amount of substance (mole), Mass (Kilogram), Electric current (Ampere). Any SI unit other than these seven is called Derived quantities, so from given options Newton which is a derived SI unit of physical quantity Force is a derived unit. Hence, the correct option is (C) Newton, is a derived unit.
The term SI stands for International system of units, which is made to establish the common reference of measurements of all the physical quantities. The units defined by International system of units (SI units) are accepted by all the countries and use these standard units for measurement of all the physical quantities in scientific fields.