Introduction to SI Units List
Physical quantities were measured in terms of standardized values called units.
For Example - In this picture below,
Length of a road- a physical quantity
Expressed in kilometers or meters- km/m are units.
If units are not clearly mentioned, then it could be difficult to compare the measured values elaborately.
Units are measured in two ways- SI units (metric system) and English units (imperial system)
The English system is widely used in the US. In the present times, every country has accepted SI units as standardized units, so mathematicians and scientists are accepting SI units as the universal method.
The International System of Units (SI) is defined as a metric system that is used as a measurement standard accepted globally. SI unit is derived from the French word Systeme International. It plays a vital role in developing scientific and technical research to avoid confusion within units. It consists of 7 base units that define 22 derived units. The quantities are defined with the power of 10, ranging from 10-24 to 1024. It is expressed as fractional or standard quantities.
Listed Below is The Table Which Represents SI Units
List of SI Units
SI units are used in physics to express different quantities which are classified to:
Basic units and Derived units.
SI Basic Units
Basic units are known as the fundamental units which are mostly used as the building block of the system of units and then the other units can be derived from SI basic units.
List of SI Basic units
There are 7 SI basic units. These units are interdependent with each other mutually stating Base Units. Each unit along with its SI units, symbol, and expressions are given below:
SI Derived Units:
There are only limited derived units that form different operations over the base units. In the case of derived units, the dimensions are expressed related to the dimensions of the base units. It can also be expressed by combining base and derived units.
List of SI Derived Units
These SI units are mostly used units. Other than these there are certain units feature mostly seen in physics such as
SI unit of velocity is meter per second (m/s)
SI unit of heat is the unit joule.
SI unit of momentum is kilogram meter per second (kg.m/s)
The SI unit of the magnetic field is Tesla.
There are numerous numbers, terms and quantities studied in physics which are expressed in various units. One must know the CGS and the SI units frequently to ace in physics.
Advantages of CGS Units and SI Units
SI units and CGS units questions are very common in physics examinations
The units and explanations can help to get into the depth of different topics.
These are provided in an interactive manner to understand easily.
These units are provided in points so that the concept will remain clear for a longer time.
Units of Measurement for Length, Time, Mass And Volume
1.Length
The SI unit of length is a meter. It is defined as the length traveled by night in a path is 1/299792458 seconds.
(Image to be added soon)
Some other units of length include nanometres, millimeters, decimeters, centimeters, meters, kilometers.
Non-SI units of length include yard, inch, foot.
2. Time
The SI unit of time is second. It can be considered as the time-taken, which is equal to 9192631770 vibrations of radiation to the distance between two hyperfine intervals of the cesium-133 atom. Time is a continuous process of existence to the future, present, and past. To know about the existence of any being, units of time are considered. The units of time are an hour, minute, and second.
Units of time are
Minute = 60 seconds
Hour = 60 minutes
Day = 24 hours
Week = 7 days
Month = 28 to 31 days
Year = 365 /366 days
3.Mass
One thing you must keep in mind is that mass is different from weight. Mass is defined as the quantity of matter in an object. The most used units for the measurement of mass are gram and kilogram.
SI unit of mass is the kilogram (kg)
Other units of mass are
Milligram = 1/1000g
Decigram = 1/10g
Centigram = 1/100g
Gram = 1000 milligrams
Decagram= 10 grams
Hectogram = 100 grams
Metric ton =1000 kilograms
Kilogram = 1000 grams
4.Volume
Capacity is measured by volume. To measure the capacity of an object the unit of volume is required. The SI unit of volume is measured in cubic meters.
1m3= 1m × 1m × 1m
Some Other Units Of Volume Are
What does SI Unit mean?
The International System of Units, abbreviated as SI Units, is a system of units of measurement that has been internationally recognised. It is the only system that has been recognised in this manner and is therefore used wherever the metric system is adopted. It is also used worldwide in scientific research.
The system is based on seven units that are known as the Base SI Units. From these Base SI Units, there have been 22 more units derived, giving them the name Coherent Derived SI Units, or simply Derived SI Units.
The seven Base SI Units are the Second for Time, the Metre for Length, the Ampere for Electric Current, the Candela for Luminous Intensity, the Mole for Amount of Substance, the Kilogram for Mass, and the Kelvin for Thermodynamic Temperature.
The 22 Coherent Derived SI Units are as follows:
Hertz for Frequency
Joule for Energy, Work, Heat
Pascal for Pressure, Stress
Radian for Angle
Steradian for Solid Angle
Coulomb for Electric Charge
Newton for Force
Ohm for Electric Resistance
Volt for Voltage
Farad for Electrical Capacitance
Siemens for Electrical Conductance
Tesla for Magnetic Induction
Henry for Electrical Inductance
Degree Celsius for Temperature relative to degree Kelvin
Weber for Magnetic Flux
Gray for Absorbed Dose of Ionising Radiation
Lumen for Luminous Flux
Lux for Illuminance
Becquerel for Radioactivity
Katal for Catalytic Activity
Sievert for Equivalent Dose of Ionising Radiation
As you can see, the Derived SI Units and the quantities they represent are connected to or based on the seven Base SI Units.
Together, the seven Base SI Units plus the 22 Coherent Derived SI Units form the collective International System of Units. This system of units is used all over the world in scientific research and study. Most of these units are also used in most of the world for regular, day-to-day use. For example, most countries in the world use the metre and kilometre as measures of distance and length, while only a few countries use miles as the main measurement of distance and length.
FAQs on SI Units List
1. What exactly are SI units?
SI units are part of the International System of Units, which is the modern standard for measurement used worldwide. Think of it as a universal language for science, industry, and trade, ensuring that a 'kilogram' or a 'metre' means the same thing in every country.
2. What is the main difference between fundamental and derived SI units?
The main difference is that fundamental units are the basic building blocks of measurement, while derived units are created by combining these fundamental units. For example:
- A fundamental unit is the metre (for length) or the second (for time).
- A derived unit is metres per second (m/s) for speed, which is created by combining the units for length and time.
3. What are the seven fundamental (or base) SI units?
The seven fundamental SI units form the foundation for all other measurements. They are:
- Metre (m) for length
- Kilogram (kg) for mass
- Second (s) for time
- Ampere (A) for electric current
- Kelvin (K) for thermodynamic temperature
- Mole (mol) for the amount of a substance
- Candela (cd) for luminous intensity
4. Why is it so important for scientists and engineers to use a standard system like SI?
Using a standard system is crucial for global collaboration and safety. When everyone uses the same units, it prevents confusion and costly errors. It ensures that experimental results can be replicated and compared accurately by people anywhere in the world, and that parts manufactured in one country will fit products assembled in another.
5. What are some key rules to follow when writing SI units and their symbols?
To write SI units correctly, remember these simple rules:
- Unit symbols are written in lowercase, unless they are named after a person (e.g., m for metre, but W for watt).
- Symbols are never pluralised. You write 10 kg, not 10 kgs.
- Always leave a space between the number and the unit symbol (e.g., 25 m).
- Unit names, when written in full, always start with a lowercase letter, even if named after a person (e.g., newton, pascal).
6. How are SI units used in our daily lives?
You use SI units more often than you might think! For example:
- When you buy groceries, vegetables are weighed in kilograms.
- The electricity you use at home is measured in kilowatt-hours, which is derived from the joule.
- Medicines often state their dosage in milligrams or millilitres, which are sub-units of the kilogram and metre.
- Weather reports often give temperatures in degrees Celsius, which is directly related to the SI unit Kelvin.
7. What does it mean for the SI system to be 'coherent'?
A 'coherent' system means that all derived units are obtained by simply multiplying or dividing the base units, with no extra numbers or conversion factors needed. For example, the unit for force (the newton) is directly defined as 1 N = 1 kg⋅m/s². This coherence makes scientific and engineering calculations much simpler and less prone to error.
