Constants In Physics

Constants in physics are synonymous with physical constants sometimes Universal constants or fundamental physical constants are the physical quantity or entity which are believed to have a constant value in time and are universal.

Table of Contents

Nature Of Physical Constants

Based on nature, the fundamental constants are grouped into three categories namely-

  • A: Characteristic of a particular system. (Characteristic of light)
  • B: Characteristic of a class of physical phenomena. (Characteristic of electromagnetic phenomena)
  • C: Universal Constants. (Discovered after the discovery of special relativity)

Few Physical constants can take the dimensional form like – the speed of light; in contrast, few are dimensionless like- fine structure constant. Some physical constants are material constants which means they possess constant value for a material.

A constant can be expressed using multiple equivalent units like – SI, natural units, atomic mass unit, CGS units etc. Some physical constants are redefined by fixing the SI values. But this certainly increases the uncertainty in the value of physical constants.

Number Of Fundamental Constants

There is no ground rule defining the number of physical constants in physics. The number varies in accordance with the accepted physical theory.

The table given below comprises the list of physical constants –

Fine-Structure Constant

Rydberg constant

Bohr radius

Electron mass

Compton wavelength

Proton mass

Neutron mass

Deuteron Mass

Alpha Particle Mass

Faraday Constant

Stefan-Boltzmann Constant

Boltzmann Constant

Gas Constant

Impedance Of Free Space

Curie Constant

Speed of light

Frequently Asked Questions – FAQs


What is the deuteron mass in amu?

The deuteron mass in amu is m = 2.013553212745(40) u.

The Curie constant is represented using which alphabet?

The Curie constant is represented using the alphabet ‘C’.

How can Curie constant be expressed in Gaussian units?

In Gaussian units, the Curie constant can be expressed as:
\(\begin{array}{l}C = \frac{\mu^2_B }{3k_B}ng^2J(J+1)\end{array} \)
C is the Curie constant.
n is the number of magnetic atoms per unit volume.
g is the g-factor.
μB is the Bohr magneton.
kB is the Boltzmann constant.
J is the angular momentum quantum number.

What is the value of Stefan-Boltzmann’s constant?

Stefan Boltzmann Constant σ = 5.670367 ×10-8W⋅m-2.K-4

What is the value of the Gas constant (R)?

The gas constant value is given by R = 8.3144598J.mol-1⋅K-1

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