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General Information, Facts & Tables
[Physics Symbols]

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Overview

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The commonly used quantities, constants and variables have been assigned symbols to assist in making the notation of formulae more concise. All symbols are typically displayed using the "italic" or "oblique" typeface. While the font face for normal characters is not specifically defined, typefaces that have serif's (ornaments at the end of each line of the character) should be used as the differences between similar characters are more pronounced. eg In "Arial", the characters "1" (numeral 1), "l" (lower case L), "I" (upper case i), and the vertical bar "|" can easily be confused.

See Also: Metric Measurement System
 

Legend

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Because some quantities are combinations of categories, a clear categorisation system is not possible, however, the following colour code has been used as a guide to assist in locating related symbols, based on their most prominent attribute..Some symbols have multiple assignments, in which case they should be taken in the context of the equation / formula that they are contained in.
 

Legend

Angle

Acoustics

Calculus / Math / Geometry

Mass / Density

Electrical

Finance

Magnetic

Heat / Temperature

Illumination

Length / Area / Volume

Mechanics

Nuclear

Power / Force / Energy

Material Strength Optics

Statistics / Probability

Time

Unspecified / Generic

Viscosity

Fluid Flow

 

 

Symbols (by Quantity)

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Quantity

Symbol

Unit(s)

Unit(s) Symbol

Absorbed dose

D

gray

Gy

Absorbed dose rate

D

röntgen

R

Activity of a radioactive substance

A

becquerel

Bq

Acceleration (gravity / free fall)

g

metre per second squared

m/s2 

Acceleration (centrifugal)

act

metre·per second squared

m/s2

Acceleration (Linear)

a

metre·per second squared

m/s2

Admittance

Y

sievert

S

Altitude above sea level

z

metre

m

Amount of substance

n

mole

mol

Angle (plane)

a, b, q, f ...

radian

rad

Angle (solid)

W, w

steradian

sr

Angle of phase difference (phase angle)

j

degrees

º

Angle of rotation

j

radian

rad

Angular acceleration

a

radian·per second squared

rad/s2

Angular frequency

w

per second

s-1

Angular momentum

L

newton·metre·second

N·m·s

Angular velocity

w

radian·per second

rad/s

Area

A

square metre

m2

Area (cross sectional)

A, q

square metre

m2

Area (of base)

Ab

square metre

m2

Area (of side)

As

square metre

m2

Area (second moment of)

I

metre4

m4

Bending stress

dbF

newton per square millimetre

N/mm2

Bulk modulus
 

K

newton·metre-2,
pascal

N·m-2,
Pa

Capacitance (electric)

C

farad

F

Capacity
 

V

litre
metre3

l
m3

Coefficient of friction

m

-

-

Coefficient of linear expansion

a

ºCelcius-1

ºC-1

Compression strength

Rdm

newton per square millimetre

N/mm2

Compression-tension fatigue limit

dzdw

newton per square millimetre

N/mm2

Conductance (electrical)

G

siemens

S

Conductance (thermal)

hl

kilowatt·metre-2·Kelvin-1

kWt·m-2·K-1

Conductivity (electrical)

a

reciprocal ohm·metre

1/(W·m)

Cubical expansion coefficient

b

ºCelcius-1

ºC-1

Current (electrical)

I

ampere

A

Current density

J

ampere·per square millimetre

A/mm

Density

r

kilogram per cubic·metre

kg/m3

Depth of fluid

h

metre

m

Diameter

d

metre

m

Dielectric constant

e

farad per metre

F/m

Dielectric displacement

D

coloumb per square metre

C/m2

Distance

a, s, t

metre

m

Dose equivalent

Dq

sievert

Sv

Dryness fraction

x

-

 

Efficiency

h

-

-

Elastic elongation or compression / strain

e

percentage

%

Elastic limit under bending

dbW

newton·per square millimetre

N/mm2

Elastic limit under torsion

ttf

newton per square millimetre

N/mm2

Elastic shear

g

radian

rad

Elasticity (modulus of / Youngs)

E

newton·per square millimetre

N/mm2

Elasticity (modulus of shear)

G

newton·per square millimetre

N/mm2

Electric field constant

e0

farad per metre

F/m

Electric field strength

E

volt·per metre

V/m

Electric flux

f, Q

ampere

A

Electric flux density

D

coulomb per square metre

C/m2

Electric potential

j

volt

V

Electric polarisation

M

coulomb per square metre

C/m2

Electrochemical equivalent

k

kilogram per coulomb

kg/C

Elongation at fracture

d, A

percentage

%

Emissivity

e

-

-

Endurance / fatigue limit

dd

newton·per square millimetre

N/mm2

Energy (internal)

U, E

joule

J

Energy (kinetic)

EK

joule

J

Electric potential

U, EP

volt

V

Energy (work)

W

joule

J

Energy (specific internal)

u, e

kilojoule·kilogram-1

kJ·kg-1

Enthalpy (heat constant)

H

joule

J

Enthalpy (specific)

h

kilojoule·Kelvin-1

kJ·K-1

Entropy

S

joule·per kelvin

J/K

Equivalent continuous sound level (A weighted)

LAeq

decibel (A)

dB (A)

Fatigue limit under reversed bending stresses

t

newton·per square millimetre

N/mm2

Fatigue limit under reversed torsional stress

ttW

newton per square millimetre

N/mm2

Fatigue strength reduction factor

bk

-

-

Field strength (electric)

E

volt·per metre

V/m

Field strength (magnetic)

H

ampere per metre

A/m

Flow rate

Q

cubic metre per second

m3/s

Flow velocity

v

metre per second

m/s

Flux density (electric)

D

coulomb per square metre

C/m2 

Flux density (magnetic) (magnetic induction)

B

tesla

T

Flux (electric)

y

coulomb

C

Flux (magnetic)

F

weber

Wb

Force

F

newton

Force (buoyancy)

Fa

newton

N

Force (acting on bottom)

Fb

newton

N

Force (acting on sides)

Fs

newton

N

Force (centrifugal)

FCT

newton

N

Force (resisting)

R

newton

N

Frequency

ƒ

hertz

Hz

Gibbs' function

G

 

J

Gibbs' function (specific)

g

 

kJ·kg-1

Heat capacity (specific)

c

 

kJ·kg-1·K-1

Heat flow rate (see power)

Q , F

watt

W

Heat flux intensity

f

kilowatt per square metre

kW/m2

Heat transmission (transfer) coefficient

k, a

watt per square metre kelvin

W/(m2·K)

Height

h

metre

m

Illumination (illuminance)

E

lux

lx

Impedance

Z

W

 

Inductance (electrical / magnetic / self)

L

henry

H

Inductance (mutual)

M

 

H

Internal energy

U, E

 

J

Internal energy (specific)

u, e

 

kJ·kg-1

Inertia (moment of)

I, J

 

kg·m2

Ion dose

J

coulomb per kilogram

C/kg

Ion dose rate

J

ampere per kilogram

A/kg

Kinematic viscosity
 

v

 

m2·s-1
St

Length

l

metre

m

Length of path

s

metre

m

Light (velocity of)

c

metre per second

m/s

Light (wavelength of)

l

 

m

Limit stress

dgr

newton per square millimetre

N/mm2

Linear expansion coefficient

c

per degree Celsius

ºC-1

Linear momentum

p

newton·second

N·s

Load (knife edge)

q

newton per millimetre

N/mm

Luminance

L

candela per square metre

cd/m2

Luminous emittance

M

lumen per square metre

lm/m2

Luminous efficiency

h

lumen per watt

lm/W

Luminous energy

Q

lumen second

lm·s

Luminous flux

F

lumen

lm

Luminous intensity

I

candela

cd

Magnetic field constant

U0

henry per metre

H/m

Magnetic field strength

H

ampere per metre

A/m

Magnetic flux

F

weber

Wb

Magnetic flux density

B

tesla

T

Magnetic polarisation

J

tesla

T

Magnetomotive force

F

ampere

A

Mass

m

kilogram

kg

Mass (flow rate)

m

kilogram per second

kg/s

Maximum deflection

s

millimetre

mm

Modulus (bulk)

K

newton per square metre

N/m

Modulus of elasticity

E

newton per square metre

N·m

Modulus of rigidity

G

newton per square metre

N/m

Modulus of section

Z

cubic metre

m3

Molar mass of gas

M

 

kg·K-1·mol-1

Molar gas constant

R

joule per mole kelvin

J(mol·K)

Molar volume

Vm

 

m3·K-1·mol-1

Moment (bending)

Mb

newton-millimetre

N·mm

Moment of force (torque)

M

newton-metre

N·m

Moment of inertia

I, J

kilogram·square metre

kg·m2

Moment of inertia (axial)

Ia

quad millimetre

mm4

Moment of inertia (polar)

Ip

quad millimetre

mm4

Moment of turning (torque)

Mt

newton millimetre

N·mm

Mutual inductance

M

henry

H

Number of turns in winding

N, w

-

-

Particle velocity

u

meter per second

m/s

Periodic time

T

second

s

Permeability (absolute)

µ

henry per minute

H/m

Permeability (absolute of free space)

µo

 

µH·m-1

Permeability (relative)

µr

-

-

Permeance

L

 

H

Permittivity (absolute)

e

 

pF·m-1

Permittivity (of free space)

eo

 

pF·m-1

Permittivity (relative)

er

-

 

Poissons' ratio

v

-

 

Polar moment of area

J

metre4

m4

Power (see heat flow rate)

P

watt

W

Power (apparent)

Ps

volt·ampere

V·A

Power (active)

P

watt

W

Power (reactive)

Pq

volt·ampere

V·A

Pressure
 

p
 

newton·per square metre
Pascal

N/m2
Pa

Pressure (absolute)
 

pabs

newton·per square metre
pascal

N/m2
Pa

Pressure (atmospheric)
 

pamb

newton·per square metre
pascal

N/m2
Pa

Pressure (fluid)

p

pascal

Pa

Pressure (gauge)
 

pq

newton·per square metre
pascal

N/m2
Pa


Quantity of heat


Q
 

watt-second
kilowatt-hour
electron-volt

W·s
kW·h
eV

Quantity of electricity
(electric charge)

Q

ampere-hour
coulomb

A·h
C

Radius

r

metre

m

Radius of curvature (neutral axis)

R

mm

mm

Radius of gyration

i

metre

m

Rating sound level (A weighted)

Ir

decibel (A)

dB (A)

Reactance

X

ohm

W

Reluctance
 

S

henry
ampere per·weber-1

H
A/Wb

Relative permittivity

er

-

-

Resistance (electrical)

R

ohm

W

Resisting force

R

newton

N

Resistance temperature coefficient

a, b, c

Celsius

C-1

Resistivity

r

ohm·metre

W··m

Resistivity (conductors)

r

megaohm·millimetre

MW·mm

Resistivity (insulators)

r

megaohm·millimetre

MW·mm

Resonant frequency

ƒr

hertz

Hz

Reverberation time

T

second

s

Rotational frequency

n

per second

s-1

Safety factor

S

-

-

Second moment of area

I

metre4

m4

Section of modulus under bending

Wb

cubic millimetre

mm3

Section of modulus under torsion

Wt

cubic millimetre

mm3

Self inductance

L

henry

H

Shear strain

g

-

 

Shear stress (mechanical)
 

s t

newton per square metre
Pascal

N/m2
Pa

Sound absorbent coefficient

a

unit

1

Sound intensity

I

watt per square metre

Wm2

Sound intensity level

Il

decibel

dB

Sound power

P

watt

W

Sound pressure

p

pascal

Pa

Sound power level (A weighted)

IWA

decibel (A)

dB (A)

Sound pressure level (A weighted)

Ipa

decibel (A)

dB (A)

Specific gas constant

Ri

joule per kilogram kelvin

J/(kg·K)

Specific acoustic impedance

Z

pascal second per metre

Pa·s/m

Specific heat capacity

c

joule per kilogram Kelvin

J/kg·K

Specific volume

v

cubic metre per kilogram

m3/kg

Strain (direct)

e

-

-

Stress amplitude

dbB

newton per square millimetre

N/mm2

Stress concentration factor #1

ak

-

-

Stress concentration factor #2

da

newton per square millimetre

N/mm2

Stress (direct)
 

s

newton·metre-2
pascal

N·m-2
Pa

Shear (modulus of rigidity)
 

G

newton·per square metre
pascal

N/m2
Pa

Surface area

S

square·metre

m2

Surface tension

c

newton per·metre

N/m

Susceptance

B

sievert

S

Temperature value

q

degree Celsius

ºC

Temperature resistance coefficients

a, b, c

per Celsius

C-1

Tensile strength

Rm

newton per square millimetre

N/mm2

Thermal conductivity

l

watt per metre·kelvin

W/m·K

Thermodynamic temperature value
 

T
t

kelvin
degree Celsius

K
ºC

Thermodynamic temperature difference
 

DT
Dt

kelvin
degree Celsius

K
ºC

Time

t, z

second

s

Torque

T

newton·metre

N·m

Torsional strength

ttB

newton per square millimetre

N/mm2

Torsional (shear) stress

tt

newton per square millimetre

N/mm2

Torsional stress limit

tgr

newton per square millimetre

N/mm2

Vapour velocity

C

metre·per second

m/s

Velocity

u

metre·per second

m·s-1

Velocity (angular) #1

w

radians·second-1

rad·s-1

Velocity (angular) #2
 

N

revolutions / second
revolutions / minute

rev/s
rev/min

Velocity of light

c

metre·second-1

m·s-1

Velocity of sound

c, cs

metre·second-1

m·s-1

Voltage (electrical)

U, V

volt

V

Voltage (magnetic)

V

ampere

A

Volume

V

cubic metre

m3

Volumetric flow rate

V

cubic metre per·second-1

m3/s

Viscosity (dynamic)

h

pascal second

Pa·s

Viscosity (kinematic)

v

square metre per·second-1

m2/s

Wavelength

l

metre

m

Wave number
 

 

reciprocal metre
 

m-1
1/m

Weight

G

newton

N

Work (energy)

W

joule

J

Wrap angle

e

radian

rad

Yield point

Re

newton per square millimetre

N/mm2

Youngs' modulus of elasticity
 

E

newton per square metre
pascal

N/m2
Pa

 

Notes

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The symbols in the table above require that the "symbol" font is installed on the computer system.