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Physical Quantities and Units | Physical Quantity Definition

Physical Quantity Definition

A physical quantity is characterized by defining how it is measured or by expressing how it is computed from other measurements. For instance, distance and time are expressed by defining methods for evaluating them, while we express average speed by stating that it is computed as distance traveled divided up by time covered.

Four fundamental physical quantities (length, time, mass, and electric current) are utilized in order to express almost all physical quantities.

Physical quantities are expressed in terms of units, which are standard values. For instance, the length of a race (a physical quantity) can be defined in units of meters. Without standard units, it would be highly challenging to define and equate measured values in a purposeful way. 

There are two leading units systems practiced globally: SI units (i.e. metric system) and English units (i.e. imperial system). English units were historically used by the British Empire and are still extensively utilized in the United States. Almost every other country on the planet practices SI units. The acronym “SI” is inferred from the French word Système International.

Physical QuantitySI UnitSymbol
LengthMeterm
TimeSeconds
CurrentAmpereA
AdmittanceSiemenS
AngleRadianRad
Angular VelocityRadian per secondRad/s
Apparent powerVolt-AmpereVA
AreaSquare meter${{m}^{2}}$
CapacitanceFaradF
ChargeCoulombC
ConductanceSiemenS
Electric Field IntensityVolt per MeterV/m
Electric FluxCoulombC
Electric Flux DensityCoulomb per Meter Square$\frac{C}{{{m}^{2}}}$
Energy Joule J
Force Newton N
Frequency hertz Hz
Impedance Ohm$\Omega $
Inductance Henry H
Magnetic Flux intensity Ampere per Meter A/m
Magnetic Flux Weber Wb
Magnetic Flux Density Tesla T
Magneto motive Force Ampere-Turn At
Moment of Inertia Kilogram Meter Square $kg.{{m}^{2}}$
Power WattW
Pressure PascalPa
Reactance Ohm$\Omega $
Reactive Power Volt-Ampere Reactive VAR
Resistance Ohm$\Omega $
ResistivityOhm-Meter $\Omega m$
Susceptance Siemen S
Torque Newton-MeterNm
Voltage Volt V
Volume Meter Cube${{m}^{3}}$

About Ahmad Faizan

Mr. Ahmed Faizan Sheikh, M.Sc. (USA), Research Fellow (USA), a member of IEEE & CIGRE, is a Fulbright Alumnus and earned his Master’s Degree in Electrical and Power Engineering from Kansas State University, USA.

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