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ohm

Also known as Ω

The ohm (symbol: Ω, the uppercase Greek letter omega) is the unit of electrical resistance in the International System of Units (SI). It is named after German physicist Georg Ohm (1789–1854). Various empirically derived standard units for electrical resistance were developed in connection with early telegraphy practice, and the British Association for the Advancement of Science proposed a unit derived from existing units of mass, length and time, and of a convenient scale for practical work as early as 1861.

AI overview

An ohm is the standard unit used to measure electrical resistance, which is the opposition that a material presents to the flow of electric current. It matters because it provides a common way to quantify and compare how much different materials and components resist electricity, making it essential for designing and understanding electrical systems.

AI-generated from the Wikipedia summary — may contain errors.

Key facts

Unit.symbol: Ω
Unit.name: ohm
Unit.image: 240px
Unit.caption: A laboratory one-ohm standard resistor,
Unit.standard: SI
Unit.quantity: electrical resistance
Unit.namedafter: Georg Ohm
Unit.units1: SI base units
Unit.inunits1: kg⋅m2⋅s−3⋅A−2

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Wikidata facts

Image: 3 Resistors.jpg

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NCI Thesaurus ID: C42554
unit symbol: Ом
conversion to SI unit: 1
Wikidata SPARQL query equivalent: wd:Q47083 p:P2370/psn:P2370 [wikibase:quantityAmount ?source; wikibase:quantityUnit ?base]. ?item p:P2370/psn:P2370 [wikibase:quantityAmount ?target; wikibase:quantityUnit ?base]. BIND(?source / ?target as ?value)
Commons category: Ohm (unit)

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~15 min read

Article

10 sections

Contents

Definition
Relation to conductance
Power as a function of resistance
History
Historical units of resistance
Realization of standards
Symbol
See also
Notes and references
External links

Following the 2019 revision of the SI, in which the ampere and the kilogram were redefined in terms of fundamental constants, the ohm is now also defined as an exact value in terms of these constants.