Ohm

<p>The ohm (symbol: Ω, the uppercase Greek letter <a href="/facts/Omega/1CrSPtKM">omega</a>) is the unit of <a href="/facts/Electrical_resistance/hxSt0UAj">electrical resistance</a> in the <a href="/facts/International_System_of_Units/S7YLglNz">International System of Units (SI)</a>. It is named after German physicist <a href="/facts/Georg_Ohm/C9AXNDAg">Georg Ohm</a> (1789–1854). Various empirically derived standard units for electrical resistance were developed in connection with early <a href="/facts/Telegraphy/JhRYDSDu">telegraphy</a> practice, and the <a href="/facts/British_Association_for_the_Advancement_of_Science/q1DLURYh">British Association for the Advancement of Science</a> proposed a unit derived from existing units of mass, length and time, and of a convenient scale for practical work as early as 1861.
</p><p>Following the <a href="/facts/2019_revision_of_the_SI/g0h07jCX">2019 revision of the SI</a>, in which the <a href="/facts/Ampere/MScqkCgz">ampere</a> and the <a href="/facts/Kilogram/lU2zbPk8">kilogram</a> were redefined in terms of fundamental constants, the ohm is now also defined as an exact value in terms of these constants.
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Ohm open-in-new

Ohm