3. International Unit System SI:International Unit System

The International Unit System (SI) is a consistent unit system that considers both the fundamental unit and the derived unit as elements.

Electricity related SI derived unit
physical quantity Unit Unit Symbol

Time

Second

S

Length

Metre

m

Mass

kilogram

kg

Electric current

ampere

A

Temperature

kelvin

K

Amount of material

mole

mol

Brightness

candela

cd

Plane angle

radian

rad

Solid angle

steradian

sr

Example of derived unit
Physical quantity Unit Unit Symbol Representation of SI Base Units Representation of other SI Units

Area

Square meter

Cubic volume

Cubic meter

Density

Kilogram/Cubic meter

Velocity, Speed

Meter/Second

m/s

Accelerated velocity

Angular velocity

Radian/Second

rad/s

Electrical current density

Ampere/Square meter

Magnetic field intensity

Ampere/Meter

A/m

Magnetomotive force, magnetic potential difference

Ampere

A

Molar concentration

Mole/Cubic meter

Brightness

Candela/Square meter

Wave number

1/Meter

Amount of radiation exposure

Coulomb«/Kilogram

C/kg

Kinetic viscosity

Square meter/Second

Number of vibration

Cycles per second

Hz

Electrical charge, electric charge

Coulomb

C

s·A

Force

Newton

N

Celsius temperature

degrees C

K

Radioactivity

Becquere

Bq

Moment of force

Newton/meter

Surface tension

Newton/meter

N/m

Viscosity

Pascal/second

Surface density of heat flow rate/ incident radiant flux density

Watt/Square meter

Thermal capacity/entropy

Joule/Kelvin

J/K

Specific heat/mass entropy

Joule/(kilogram ?E Kelvin)

Thermal conductivity

Watt/(Meter Kelvin)

Electrical field intensity

Bolt/meter

V/m

Dielectric displacement / dielectric displacement

Coulomb/square meter

Dielectric constant

Farad/meter

F/m

Magnetic permeability

Henry/meter

Absorbed dose

Gray

Gy

J/kg

Dose equivalent

Sievert

Sv

J/kg

Pressure, stress

Pascal

Pa

Energy, work, and amount of heat

Joule

J

N·m

Power, electrical power

Watt

W

J/s

Electrical voltage, electric potential

Bolt

V

W/A

Capacitance

Farad

F

C/V

Electrical resistance

Ohm

Ω

V/A

Conductance

Siemens

S

A/V

Flux

Weber

Wb

V·s

Magnetic flux density

Tesla

T

Inductance

Henry

H

Wb/A

Light flux

Lumen

lm

cd·sr

Illuminance

Lux

lx

lm/m