This page documents an OPTIMADE Unit Definition. See https://schemas.optimade.org/ for more information.

**ID: https://schemas.optimade.org/defs/v1.2/units/si/2019/named/ohm**

`ohm`

**Unit name:** ohm

**Latin symbol:** ohm

**Display symbol:** Ω

**Description:** A derived SI unit for electrical resistance equal to kg·m²·s⁻³·A⁻² in the 2019 SI units.

"The ohm is the electrical resistance that exists between two points of a conductor when a constant potential difference of one volt, applied between these two points, produces a current of one ampere in the conductor, provided that the conductor is not the seat of any electromotive force." [9th CGPM meeting in 1946]

The ohm was defined at the 9th CGPM Meeting in 1946, included in SI at the 11th CGPM meeting in 1960, resolution 12, implicitly redefined via the redefinitions of the second at the 13th CGPM Meeting in 1967, resolution 1, the metre at the 17th CGPM meeting (1983), resolution 1, and the kilogram and ampere at the 26th CGPM Meeting (2018), resolution 1.

**Resources:**

- Definition at the 9th CGPM meeting (1948)
- Definition and establishment of the SI unit system at the 11th CGPM meeting (1960), resolution 12.
- Redefinition of the metre at the 17th CGPM meeting (1983), resolution 1
- Redefinition of the second in the 13th CGPM Meeting (1967), resolution 1
- Redefinition of the kilogram and the ampere at the 26th CGPM Meeting (2018), resolution 1
- Wikipedia article describing the unit

**JSON definition:**

```
{
"$id": "https://schemas.optimade.org/defs/v1.2/units/si/2019/named/ohm",
"$schema": "https://schemas.optimade.org/meta/v1.2/optimade/physical_unit_definition.json",
"title": "ohm",
"symbol": "ohm",
"display-symbol": "\u03a9",
"description": "A derived SI unit for electrical resistance equal to kg\u00b7m\u00b2\u00b7s\u207b\u00b3\u00b7A\u207b\u00b2 in the 2019 SI units.\n\n\"The ohm is the electrical resistance that exists between two points of a conductor when a constant potential difference of one volt, applied between these two points, produces a current of one ampere in the conductor, provided that the conductor is not the seat of any electromotive force.\" [9th CGPM meeting in 1946]\n\nThe ohm was defined at the 9th CGPM Meeting in 1946, included in SI at the 11th CGPM meeting in 1960, resolution 12, implicitly redefined via the redefinitions of the second at the 13th CGPM Meeting in 1967, resolution 1, the metre at the 17th CGPM meeting (1983), resolution 1, and the kilogram and ampere at the 26th CGPM Meeting (2018), resolution 1.",
"resources": [
{
"relation": "Definition at the 9th CGPM meeting (1948)",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/9-1948"
},
{
"relation": "Definition and establishment of the SI unit system at the 11th CGPM meeting (1960), resolution 12.",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/11-1960/resolution-12"
},
{
"relation": "Redefinition of the metre at the 17th CGPM meeting (1983), resolution 1",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/17-1983/resolution-1"
},
{
"relation": "Redefinition of the second in the 13th CGPM Meeting (1967), resolution 1",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/13-1967/resolution-1"
},
{
"relation": "Redefinition of the kilogram and the ampere at the 26th CGPM Meeting (2018), resolution 1",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/26-2018/resolution-1"
},
{
"relation": "Wikipedia article describing the unit",
"resource-id": "https://en.wikipedia.org/wiki/Ohm"
}
],
"defining-relation": {
"base-units": [
{
"symbol": "A",
"id": "https://schemas.optimade.org/defs/v1.2/units/si/2019/base/ampere"
},
{
"symbol": "kg",
"id": "https://schemas.optimade.org/defs/v1.2/units/si/2019/base/kilogram"
},
{
"symbol": "m",
"id": "https://schemas.optimade.org/defs/v1.2/units/si/1983/base/metre"
},
{
"symbol": "s",
"id": "https://schemas.optimade.org/defs/v1.2/units/si/1967/base/second"
}
],
"base-units-expression": "A^-2*kg*m^2*s^-3"
},
"standard": {
"name": "si",
"year": 2019,
"category": "named",
"symbol": "ohm"
},
"x-optimade-definition": {
"label": "ohm_si_2019_named",
"kind": "unit",
"format": "1.2",
"version": "1.2.0",
"name": "ohm"
}
}
```