Mho (℧) (Obsolete) Unit | All you need to know
The mho (symbol: ℧) is an obsolete unit of electric conductance equal to one siemens. Before the International System of Units (SI) adopted the siemens as the standard unit of conductance, the mho was widely used by electrical engineers and scientists. Although it has been replaced by the siemens in modern practice, the mho is still encountered in historical literature, legacy equipment documentation, and older engineering references.
What Is a Mho?
The mho (symbol: ℧) is a unit of electric conductance equal to 1 siemens. The name mho is simply the word ohm spelled backward, emphasizing that conductance is the reciprocal of electrical resistance. Its symbol (℧) is an inverted capital omega (Ω), the symbol used for the ohm.
Since one mho is exactly equal to one siemens, the two units represent the same physical quantity. However, the siemens is now the official SI-derived unit, while the mho is considered obsolete.
History of the Mho
The mho was introduced in the late 19th century as a convenient name for the reciprocal of the ohm. It became widely used in electrical engineering and scientific publications for many years. In 1971, the International Electrotechnical Commission (IEC) adopted the siemens as the official SI-derived unit of electrical conductance in honor of Werner von Siemens. Since then, the mho has gradually disappeared from modern technical standards.
Current Uses of the Mho
Today, the mho is considered obsolete and is rarely used in current engineering or scientific work. It is primarily encountered in older electrical textbooks, technical manuals, legacy electrical equipment, and historical engineering documents.
Mho Conversion
One mho is equal to:
- 1 siemens (S)
- 1,000 millisiemens (mS)
- 1,000,000 microsiemens (µS)
- 0.001 kilosiemens (kS)
You can use ChangeUnit to convert mho to siemens, millisiemens, microsiemens, and many other electric conductance units.