# 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.

## 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.

## Frequently Asked Questions – FAQs

Q1

### What is the deuteron mass in amu?

The deuteron mass in amu is m = 2.013553212745(40) u.
Q2

### The Curie constant is represented using which alphabet?

The Curie constant is represented using the alphabet ‘C’.
Q3

### How can Curie constant be expressed in Gaussian units?

In Gaussian units, the Curie constant can be expressed as:
$$\begin{array}{l}C = \frac{\mu^2_B }{3k_B}ng^2J(J+1)\end{array}$$
Where,
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.
Q4

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

Stefan Boltzmann Constant σ = 5.670367 ×10-8W⋅m-2.K-4
Q5

### 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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