Understanding the CGS Unit of Electric Current

In the International System of Units (SI), the ampere is the unit of electric current. However, in the centimeter-gram-second (CGS) system of units, there are different definitions for the unit of electric current. This article explores the CGS units of electric current and provides a detailed overview of the Biot, a unit named after the French physicist Jean-Baptiste Biot.

What is the CGS Unit of Electric Current?

There are two CGS units of electric current:

The Biot (Bi) The abampere (abA)

The Biot is named after Jean-Baptiste Biot, a famous French physicist who co-discovered the magnetic effect of electric current with Felix Savart in 1820. The Biot was originally defined as the constant current that would create a force of two dynes per centimeter between two infinitely long parallel conductors one centimeter apart in a vacuum.

The Definition of the Biot

The Biot unit is defined in the CGS system as follows:

The Biot is that constant current which, if maintained in two straight parallel conductors of infinite length of negligible circular cross-section and placed one centimeter apart in a vacuum, would produce a force of two dynes per centimeter of length between these conductors.

Related CGS Units

Other units in the CGS system related to the Biot or abampere include:

Absoult Coulomb (abcoulomb): The charge that passes in one second through any cross-section of a conductor carrying a steady current of one abampere. Absoult Henry (abhenry): The self-inductance of a circuit or the mutual inductance of two circuits in which the variation of current at the rate of one abampere per second results in an induced electromotive force of one abvolt. Absoult Ohm (abohm): The resistance of a conductor that with a constant current of one abampere through it maintains between its terminals a potential difference of one abvolt.

The SI Definition of Current

For completeness, the SI definition of current is given below:

The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length of negligible circular cross-section and placed one meter apart in a vacuum, would produce a force of 2×107 newtons per meter of length between these conductors.

This article has explored the Biot, a fundamental unit of electric current in the CGS system, and provided a clear definition of the Biot along with related CGS units. Understanding the differences between the CGS and SI systems can be particularly useful for physicists and scientists working in different fields or using different measurement systems.