Constants

This page lists various constants used in physics and some useful conversions.

Physical constants[edit]

The number in brackets represents the uncertainty in the constant, so that has an uncertainty of .

Name	Symbol	Value	Meaning	Used in	Exact
Planck's constant			It relates the frequency of a photon to its energy	Quantum mechanics	Inexact[1]
Speed of light			This is the speed of light in a vacuum	Most of physics, such as optics and relativity	Exact[2]
Permittivity of free space			Related to the strength of an electric field produced by a charge	Electromagnetism	Exact[3]
Permeability of free space			Related to the strength of magnetic fields produced by a current	Electromagnetism	Exact[4]
Elementary charge			The magnitude of the electric charge on an electron	Determines the strength of electric and magnetic fields produced by protons, electrons etc.	Inexact[5]
Avogadro's number			The number of constituents in 1 mole of something	Chemistry, statistical mechanics, thermodynamics	Inexact[6]
Ideal gas constant			Relates the pressure, volume, temperature and number of moles of an ideal gas	Thermodynamics	Inexact[7]
Faraday Constant			The electric charge on one mole of electrons (Avogadro's number times elementary charge)	Chemistry, physics	Inexact[8]
Gravitational constant			Constant related to the strength of Newtonian gravity	Newtonian gravity	Inexact[9]
Boltzmann constant			Thermodynamics		Inexact[10]
Reduced Planck's constant			Quantum mechanics	It is Planck's constant divided by .	Inexact[11]
Wien displacement constant			Relates the temperature of a black body to the peak in its spectrum		Inexact[12]
Standard acceleration due to gravity			This is the acceleration of any object near to the earth's surface when gravity is the only force acting (i.e., no air resistance).	Mechanics	Exact[13]
Proton mass			Rest mass of a proton		Inexact[14]
Neutron mass			Rest mass of a neutron		Inexact[15]
Electron mass			Rest mass of an electron		Inexact[16]

Useful Conversions[edit]

Length[edit]

1 metre = 39.37 inches 1 metre = 3.281 feet 1 kilometre = 0.6213 miles

1 mile = 5280 feet 1 mile = 1760 yards

Weight[edit]

1 kilogram = 35.27 ounce 1 kilogram = 2.205 pounds

Pressure[edit]

1 atm = 101.1 kPa 1 atm = 760 torr 1 atm = 760 mm Hg

Other[edit]

Atomic mass unit: 1.00 amu = 1.67 x 10⁻²⁷ kg

1.000 calorie = 4.184 Joules

Standard Temperature and Pressure (STP): temperature = 273 K and pressure = 1.00 atm

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Relative mass and charge of subatomic particles found in atoms.

Atomic particles

	Relative Mass	Relative Charge
Proton	1	+1
Neutron	1	0
Electron	1/1837	-1

Prefixes[edit]

Prefixes in front of a unit indicate that that unit should be multiplied by a multiple of ten, e.g. Giga is 10⁹, so 1 GPa = 10⁹ Pa.

Name	Symbol	Power
Pico	p	10−12
nano	n	10−9
micro	μ	10−6
milli	m	10−3
centi	c	10−2
deci	d	10−1
deca	da	101
hecto	h	102
kilo	k	103
mega	M	106
giga	G	109
tera	T	1012

References[edit]