CGS in physics refers to the centimetre–gram–second system of units, a variant of the metric system. This system uses the centimetre as the unit of length, the gram as the unit of mass, and the second as the unit of time.
Understanding the CGS System
The CGS system was widely used in physics and related fields before being largely superseded by the International System of Units (SI). It simplifies some calculations in certain areas of physics, particularly electromagnetism, although it can be less convenient for everyday measurements.
Key Units in CGS
Here's a breakdown of the base units in the CGS system:
- Length: Centimetre (cm)
- Mass: Gram (g)
- Time: Second (s)
Derived Units
Many other units are derived from these base units. Some important examples include:
- Force: Dyne (dyn) – 1 dyn = 1 g⋅cm/s2
- Energy: Erg (erg) – 1 erg = 1 g⋅cm2/s2
- Magnetic Field: Gauss (G)
- Magnetic Flux: Maxwell (Mx)
CGS Variants: EMU and ESU
It's important to note that within the CGS system, there are different conventions for dealing with electromagnetism. The two main variants are:
- EMU (Electromagnetic Units): This system defines the unit of electric current (abampere or biot) first and derives the unit of charge from it. It is often used in magnetism.
- ESU (Electrostatic Units): This system defines the unit of electric charge (statcoulomb or franklin) first and derives the unit of current from it. It is often used in electrostatics.
These variations can lead to different forms of equations and conversion factors compared to the SI system.
Advantages and Disadvantages
Advantages:
- Simpler formulas in certain areas of physics, especially electromagnetism.
- Historical significance; much older scientific literature uses CGS units.
Disadvantages:
- Not a coherent system (derived units not always simply related to base units).
- Less practical for everyday measurements compared to SI.
- Different electromagnetic unit variations (EMU and ESU) can be confusing.
- Conversion to SI units often required.
Transition to SI
The SI system is now the standard in most scientific and engineering fields. While CGS is still used in some specialized areas like astrophysics and certain branches of physics, its use is generally declining in favor of the more universally accepted SI system.
In summary, the CGS system is an older metric system based on the centimetre, gram, and second. While it has some advantages, it has largely been replaced by the more comprehensive and standardized SI system.
