abwatt

An abwatt is a unit of electrical power in the centimeter-gram-second (CGS) system, equal to 10-7 watts or 0.1 microwatts. It derives from the abampere, the CGS unit of current, and the abvolt, the CGS unit of voltage. One abwatt is the power dissipated when one abampere of current flows across one abvolt of potential difference. The unit appears primarily in older scientific literature, historical engineering texts, and specialized work in electromagnetic theory where CGS units remain entrenched.

The prefix ab comes from absolute, reflecting CGS conventions where electromagnetic units are defined from mechanical quantities rather than in terms of permittivity and permeability constants. The abwatt sits within a coherent system where the abampere (10 amperes in SI units) and abvolt (10-8 volts in SI units) combine naturally to give the abwatt. This dimensional consistency made CGS units valuable for theoretical work, though their relationship to practical electrical scales created persistent conversion headaches.

Practical obsolescence and residual use

The abwatt has been superseded by SI units in virtually all modern engineering and physics. Converting measurements between CGS and SI required constant vigilance: an abwatt equals 100 nanovolts times one ampere, or equivalently 10 microvolts times 10 milliamps. Industrial work abandoned CGS almost entirely after the 1970s, yet legacy papers in electromagnetics, plasma physics, and theoretical studies still reference abwatts, particularly in Russian and Eastern European technical literature where CGS lingered longer.

Practitioners today encounter the abwatt almost exclusively when consulting historical data, translating older foreign research, or working with niche academic domains. A power measurement of 1 abwatt represents an extraordinarily small amount of energy per unit time, equivalent to 0.1 microwatts, suitable only for describing phenomena at atomic or molecular scales, not for industrial equipment. Anyone working with such minute power levels would more naturally report in SI prefixes: microvolts, picoamps, nanowatts.

The term survives chiefly as a historical marker and a reminder of how technical standards evolve. Its appearance in a specification or reference signals work rooted in mid-twentieth-century physics or translation of materials predating the global shift to SI. Modern industrial practice treats the abwatt as a fossil unit, retained only in archival contexts or when fidelity to original sources demands it.