SI Units in Physics

What is the SI Unit?

SI (Système International) unit is an international system of measurements that are used universally in technical and scientific research to avoid the confusion with the units. Having a standard unit system is important because it helps the entire world to understand the measurements in one set of unit systems. Following is the table with base SI units:

Name of the Quantity	SI Unit	SI Unit Symbol
Length (l)	Meter	m
Mass (M)	Kilogram	kg
Time (T)	Second	s
Electric current (I)	Ampere	A
Thermodynamic temperature (Θ)	Kelvin	K
Amount of substance (N)	Mole	mol
Luminous intensity (J)	Candela	cd

What is SI Units List?

There are several SI units used in physics that are used to express the different quantities. The quantities can be classified into two groups i.e. base units and derived units.

SI Base Units

These are the fundamental units and are considered as the building blocks of the system. All the other units are derived from the SI Base units. One of the examples is that the SI unit of mass is kilogram. This is often confused with grams.

SI Base Units List

There are 7 SI base units. The seven units along with their SI unit and symbol are given below:

Unit of Measurment

SI Unit Description Unit of length. Meter (m). It is the base unit of length and equals roughly 39.37 inches. It is from this unit that smaller units like the centimetre and millimetre have been derived Unit of time Second (s) It is defined as the constant value of cesium frequency and is expressed as s Unit of the mass Kilogram (kg)
It is the basic SI Unit of Mass. Originally, a kilogram was meant to be exactly equal to the volume of 1000 cubic cm of water, but it is actually very slightly different Unit of electric current Ampere (A) It is defined by considering the constant value of the elementary charge.&nbsp Unit of luminous intensity Candela (cd) The luminous intensity is defined by the constant value of luminous efficacy. Unit of the amount of substance Mole (mol) It is defined by the constant value of Avogadro constant (NA) fair one mole is 6.02214076 × 1023 elementary entities. It is expressed as mol-1 Unit of thermodynamics temperature Kelvin (k) Thermodynamics temperature is defined by taking the constant value of Boltzmann constant where k = 1.38 0649 ×10-23

It should be noted that these 7 units are assumed to be mutually independent and hence are called base units.

SI Derived Units

The derived units are unlimited as they are formed by different operations on the base units. For derived units, the dimensions are expressed in terms of the dimensions of the base units. The derived units might also be expressed with the combination of base and derived units.

SI Derived Units List

There are several derived units in physics. Some of the most widely used SI derived units in physics are given below.

Unit(s) Name	SI Unit	SI Unit Symbol	Expressed in SI Base Unit	Expressed in other SI units
Force, Weight	Newton	N	kg⋅m⋅s-2	&#8211
Frequency	Hertz	Hz	s-1	&#8211
Electric charge	Coulomb	C	s⋅A	&#8211
Electric potential (Voltage)	Volt	V	kg.m2.s-3.A-1	W/A
Inductance	Henry	H	kg.m2.s-2.A-2	Wb/A
Capacitance	Farad	F	kg−1.m−2.s4.A2	C/V
Resistance, Impedance, Reactance	Ohm	Ω	kg.m2.s−3.A−2	V/A
Electrical conductance	Siemens	S	kg−1.m−2.s3.A2	Ω−1
Magnetic flux	Weber	Wb	kg.m2.s−2.A−1	V⋅s
Magnetic flux density	Tesla	T	kg.s−2.A−1	Wb/m2
Energy, Work, Heat	Joule	J	kg.m2.s−2	N⋅m = Pa⋅m3
Power, Radiant flux	Watt	W	kg.m2.s−3	J/s
Angle	Radian	rad	m.m−1	&#8211
Radioactivity	Becquerel	Bq	s-1	&#8211
Luminous flux	Lumen	lm	cd	cd⋅sr

These were a few widely used units along with their SI units. Apart from these units, there are certain additional units that are commonly seen in physics. Some of such units are:

• The SI unit of momentum (P) is kilogram meter per second (kg⋅ m/s)
• The SI unit of the magnetic field (B) is Tesla
• The SI unit of heat is the unit joule
• The SI unit of velocity is m/s

Students are suggested to be thorough with these aforementioned important physics SI units lists. In the exam, it is important to write the units and dimensions corresponding to the quantity as an answer is considered incomplete without its unit.

Various units and SI units of based articles related to physics are provided here. In physics, there are various terms and quantities. The different quantities in physics can be expressed in various units. Students who want to excel in physics must know the CGS and SI units fluently to score well in their examination. The detailed SI Units and CGS Units are given below to help students understand the respective topic in an effective manner.