Statampere Unit | All you need to know
The statampere (symbol: sA or statA) is the unit of electric current in the centimetre–gram–second (CGS) electrostatic system of units (ESU). It is defined as the flow of one statcoulomb (the CGS unit of charge) per second. Unlike the more common Ampere or even the Abampere, the statampere is an extremely small unit of current, used primarily in theoretical physics.
Statampere vs. Abampere: Two Sides of the CGS System ⚡
The CGS system for electricity and magnetism has two main branches, which can be confusing. It's important to know the difference:
- Electrostatic System (ESU): This system, which includes the statampere, is based on the electrostatic force between charges (Coulomb's Law).
- Electromagnetic System (EMU): This system, which includes the abampere, is based on the magnetic force between currents (Ampère's Force Law).
The statampere and abampere are CGS counterparts, defined from different physical principles. As a result, they have vastly different sizes.
The Scientific Definition of a Statampere
The definition of the statampere is very direct. It is based on the CGS unit of electric charge, the statcoulomb (also known as the Franklin or esu charge).
A statampere is a current in which one statcoulomb of charge flows past a point every second.
The statcoulomb itself is defined by the force it exerts: two point charges of 1 statcoulomb each, placed 1 centimeter apart, will exert a force of exactly 1 dyne on each other.
Statampere to Ampere: A Tiny Conversion
For practical use, the most critical piece of information is the statampere's relationship to the Ampere (A), the standard SI unit. The statampere is incredibly small in comparison.
- 1 Statampere (sA) ≈ 3.3356 × 10⁻¹⁰ Amperes (A)
- 1 Ampere (A) ≈ 2.9979 × 10⁹ Statamperes (sA)
To put this into perspective, to generate just one Ampere of current—roughly the amount used by a simple LED light—you would need a flow of nearly 3 billion statamperes. This clearly shows why the statampere is not used for everyday applications.
Who Uses the Statampere Today?
Much like the abampere, the statampere is a legacy unit. It is not used in any modern electrical, electronic, or engineering work. The Ampere is the universal standard.
You may encounter the statampere when reading older scientific literature or in highly specialized areas of theoretical physics, such as plasma physics or astrophysics, where calculations are sometimes still performed in the CGS system. It is a unit of historical and academic importance rather than practical use.
The Key Takeaway
The statampere is the CGS electrostatic unit for electric current. It is an extremely small unit, equivalent to only a tiny fraction of an Ampere. While it has been replaced by the SI system for all practical purposes, it remains an important part of the history of physics and the diverse systems scientists once used to measure the world.
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