# The 12 Important Physical Constants

Level 2 (without higher mathematics)
Level 2 requires school mathematics. Suitable for pupils.
Updated by Alexander Fufaev on

## Speed of light

Speed of light tells us how fast light travels in empty space (vacuum).

Value of the speed of light
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## Elementary charge

The elementary charge is the smallest, freely existing electric charge in our universe.

Value of the elementary charge
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## Vacuum permeability

The vacuum permeability appears in equations that deal with magnetic fields.

Value of the vacuum permeability
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## Vacuum permittivity

The vacuum permittivity occurs in equations that deal with electric fields.

Value of the vacuum permittivity
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## Planck's constant

The Planck's constant, is a physical constant that appears in equations whenever the equation describes quantum effects.

Value of the Planck constant
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## Gravitational constant

The gravitational constant occurs in Newton's law of gravity and Einstein field equations, which describe the interaction between masses.

Value of the gravitational constant
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## Boltzmann constant

The Boltzmann constant occurs in equations which describe systems with many particles.

Value of the Boltzmann constant
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## Electron mass

The mass of one electron

Electron mass value
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## Proton mass

Mass of one proton

Value of the proton mass
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## Neutron mass

Mass of one neutron

Value of the proton mass
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