Physical Quantity Reference

  

 Physical Quantity 

Quantity	Symbol	Used for	Unit
abasement	A	Measure of sustained displacement: the first integral with respect to time of displacement	m⋅s
Absorbed dose rate	D	Absorbed dose received per unit of time	Gy/s
Acceleration	a→	Rate of change of velocity per unit time: the second time derivative of position	m/s2
Action	S	Momentum of particle multiplied by distance travelled	J/Hz
Angular acceleration	ωa	Change in angular velocity per unit time	rad/s2
Angular momentum	L	Measure of the extent and direction of an object rotates about a reference point	kg⋅m2/s
Angular velocity	ω	The angle incremented in a plane by a segment connecting an object and a reference point per unit time	rad/s
Area	A	Extent of a surface	m2
Area density	ρA	Mass per unit area	kg⋅m−2
Capacitance	C	Stored charge per unit electric potential	farad (F = C/V)
Catalytic activity concentration		Change in reaction rate due to presence of a catalyst per unit volume of the system	kat⋅m−3
Centrifugal force	Fc	Inertial force that appears to act on all objects when viewed in a rotating frame of reference	N⋅rad = kg⋅m⋅rad⋅s−2
Chemical potential	μ	Energy per unit change in amount of substance	J/mol
Crackle	c→	Change of jounce per unit time: the fifth time derivative of position	m/s5
Current density	J →	Electric current per unit cross-section area	A/m2
Dose equivalent	H	Received radiation adjusted for the effect on biological tissue	sievert (Sv = m2/s2)
Dynamic viscosity	v	Measure for the resistance of an incompressible fluid to stress	Pa⋅s
Electric charge	Q	The force per unit electric field strength	coulomb (C = A⋅s)
Electric Current	I or i	Rate of flow of electrical charge per unit time	ampere (A)
Electric charge density	ρQ	Electric charge per unit volume	C/m3
Electric dipole moment	p	Measure of the separation of equal and opposite electric charges	C⋅m
Electric displacement field	D→	Strength of the electric displacement	C/m2
Electric field strength	E→	Strength of the electric field	V/m, N/C
Electrical conductance	G	Measure for how easily current flows through a material	siemens (S = Ω−1)
Electrical conductivity	σ	Measure of a material's ability to conduct an electric current	S/m
Electric potential	φ	Energy required to move a unit charge through an electric field from a reference point	volt (V = J/C)
Electrical resistance	R	Electric potential per unit electric current	ohm (Ω = V/A)
Electrical resistivity	ρe	Bulk property equivalent of electrical resistance	ohm-metre (Ω⋅m)
Energy	E	Energy	J
Energy density	ρE	Energy per unit volume	J⋅m−3
Entropy	S	Logarithmic measure of the number of available states of a system	J/K
Force	F→	Transfer of momentum per unit time	newton (N = kg⋅m⋅s−2)
Frequency	f	Number of (periodic) occurrences per unit time	hertz (Hz = s−1)
Half-life	t1/2	Time for a quantity to decay to half its initial value	s
Heat	Q	Thermal energy	joule (J)
Heat capacity	Cp	Energy per unit temperature change	J/K
Heat flux density	ϕQ	Heat flow per unit time per unit surface area	W/m2
Illuminance	Ev	Wavelength-weighted luminous flux per unit surface area	lux (lx = cd⋅sr/m2)
Impedance	Z	Resistance to an alternating current of a given frequency, including effect on phase	ohm (Ω)
Impulse	J	Transferred momentum	newton-second (N⋅s = kg⋅m/s)
Inductance	L	Magnetic flux generated per unit current through a circuit	henry (H)
Irradiance	E	Electromagnetic radiation power per unit surface area	W/m2
Intensity	I	Power per unit cross sectional area	W/m2
Jerk	j→	Change of acceleration per unit time: the third time derivative of position	m/s3
Jounce (or snap)	s→	Change of jerk per unit time: the fourth time derivative of position	m/s4
Linear density	ρl	Mass per unit length	kg⋅m−1
Luminous flux (or luminous power)	F	Perceived power of a light source	lumen (lm = cd⋅sr)
Mach number (or mach)	M	Ratio of flow velocity to the local speed of sound	unitless
Magnetic field strength	H	Strength of a magnetic field	A/m
Magnetic flux	Φ	Measure of magnetism, taking account of the strength and the extent of a magnetic field	weber (Wb)
Magnetic flux density	B	Measure for the strength of the magnetic field	tesla (T = Wb/m2)
Magnetic moment (or magnetic dipole moment)	m	The component of magnetic strength and orientation that can be represented by an equivalent magnetic dipole	N⋅m/T
Magnetization	M	Amount of magnetic moment per unit volume	A/m
Mass fraction	x	Mass of a substance as a fraction of the total mass	kg/kg
(Mass) Density (or volume density)	ρ	Mass per unit volume	kg/m3
Mean lifetime	τ	Average time for a particle of a substance to decay	s
Molar concentration	C	Amount of substance per unit volume	mol⋅m−3
Molar energy	J/mol	Amount of energy present in a system per unit amount of substance	J/mol
Molar entropy	S°	Entropy per unit amount of substance	J/(K⋅mol)
Molar heat capacity	c	Heat capacity of a material per unit amount of substance	J/(K⋅mol)
Moment of inertia	I	Inertia of an object with respect to angular acceleration	kg⋅m2
Momentum	p→	Product of an object's mass and velocity	kg⋅m/s
Optical power	P	Measure of the effective curvature of a lens or curved mirror; inverse of focal length	dioptre (dpt = m−1)
Permeability	μs	Measure for how the magnetization of material is affected by the application of an external magnetic field	H/m
Permittivity	εs	Measure for how the polarization of a material is affected by the application of an external electric field	F/m
Plane angle	θ	Ratio of circular arc length to radius	radian (rad)
Power	P	Rate of transfer of energy per unit time	watt (W)
Pressure	p	Force per unit area	pascal (Pa = N/m2)
Pop	p→	Rate of change of crackle per unit time: the sixth time derivative of position	m/s6
(Radioactive) Activity	A	Number of particles decaying per unit time	becquerel (Bq = Hz)
(Radioactive) Dose	D	Ionizing radiation energy absorbed by biological tissue per unit mass	gray (Gy = m2/s2)
Radiance	L	Power of emitted electromagnetic radiation per unit solid angle per emitting source area	W/(m2⋅sr)
Radiant intensity	I	Power of emitted electromagnetic radiation per unit solid angle	W/sr
Reaction rate	r	Rate of a chemical reaction for unit time	mol/(m3⋅s)
Refractive index	n	Factor by which the phase velocity of light is reduced in a medium	unitless
Reluctance		resistance to the flow of magnetic flux	H−1
Solid angle	Ω	Ratio of area on a sphere to its radius squared	steradian (sr)
Specific energy		Energy density per unit mass	J⋅kg−1
Specific heat capacity	c	Heat capacity per unit mass	J/(K⋅kg)
Specific volume	v	Volume per unit mass (reciprocal of density)	m3⋅kg−1
Spin	S	Quantum-mechanically defined angular momentum of a particle	kg⋅m2⋅s−1
Strain	ε	Extension per unit length	unitless
Stress	σ	Force per unit oriented surface area	Pa
Surface tension	γ	Energy change per unit change in surface area	N/m or J/m2
Temperature gradient		steepest rate of temperature change at a particular location	K/m
Thermal conductance	κ (or) λ	Measure for the ease with which an object conducts heat	W/K
Thermal conductivity	λ	Measure for the ease with which a material conducts heat	W/(m⋅K)
Thermal resistance	R	Measure for the ease with which an object resists conduction of heat	K/W
Thermal resistivity	Rλ	Measure for the ease with which a material resists conduction of heat	K⋅m/W
Torque	τ	Product of a force and the perpendicular distance of the force from the point about which it is exerted	newton-metre (N⋅m)
Velocity	v→	Moved distance per unit time: the first time derivative of position	m/s
Volume	V	Three dimensional extent of an object	m3
Volumetric flow rate	Q	Rate of change of volume with respect to time	m3⋅s−1
Wavelength	λ	Perpendicular distance between repeating units of a wave	m
Wavenumber	k	Repetency or spatial frequency: the number of cycles per unit distance	m−1
Wavevector	k→	Repetency or spatial frequency vector: the number of cycles per unit distance	m−1
Weight	w	Gravitational force on an object	newton (N = kg⋅m/s2)
Work	W	Transferred energy	joule (J)
Young's modulus	E	Ratio of stress to strain	pascal (Pa = N/m2)