Reciprocal Ohm (Ω⁻¹) Unit | All you need to know
The reciprocal ohm (Ω⁻¹) is a unit of electric conductance that is numerically equal to one siemens. It represents the inverse of electrical resistance measured in ohms and was commonly used before the siemens became the internationally recognized SI-derived unit of conductance. Today, it is mainly encountered in historical engineering documents and older technical publications.
What Is a Reciprocal Ohm?
The reciprocal ohm (symbol: Ω⁻¹) is a unit of electric conductance equal to 1 siemens. Since conductance is the mathematical reciprocal of electrical resistance, one reciprocal ohm corresponds to the conductance of a component having a resistance of one ohm.
The reciprocal ohm and the siemens represent exactly the same physical quantity. However, the siemens is the official SI-derived unit used in modern scientific and engineering applications.
History of the Reciprocal Ohm
Before the siemens was officially adopted by the International Electrotechnical Commission (IEC) in 1971, electrical engineers often expressed conductance using the reciprocal ohm or the closely related mho (℧). These terms clearly indicated the inverse relationship between resistance and conductance. Over time, the siemens replaced both names in international standards.
Current Uses of the Reciprocal Ohm
Today, the reciprocal ohm is rarely used in modern engineering practice. It is primarily found in historical textbooks, legacy technical documentation, older electrical instruments, and scientific literature published before the widespread adoption of the siemens.
Reciprocal Ohm Conversion
One reciprocal ohm is equal to:
- 1 siemens (S)
- 1 mho (obsolete)
- 1,000 millisiemens (mS)
- 1,000,000 microsiemens (µS)
You can use ChangeUnit to convert reciprocal ohm to siemens, mho (obsolete), millisiemens, and many other electric conductance units.