# Joule heating

`JOULE_HEATING` couples current conduction to heat conduction: it solves the steady temperature the Joule losses of the solved current produce. It reads the conditions of [Current conduction](<https://docs.femforge.io/user-guide/conditions/current-conduction/index.md>) and [Thermal](<https://docs.femforge.io/user-guide/conditions/thermal/index.md>) as well as its own, so the same tags drive the standalone and the coupled solves. See [Conditions and physics](<https://docs.femforge.io/user-guide/conditions/index.md>) for how conditions attach and where they land.

| Frame | Solves as | Solver stack |
| --- | --- | --- |
| [Solid](<https://docs.femforge.io/user-guide/frames/solid/index.md>) | `JOULE_HEATING` | StatCurrentSolver, HeatSolver, SaveScalarsSolver, ResultOutputSolver |
| [Axisymmetric](<https://docs.femforge.io/user-guide/frames/axisymmetric/index.md>) | no form |  |
| [Cartesian2D](<https://docs.femforge.io/user-guide/frames/cartesian-2d/index.md>) | no form |  |

## Boundary conditions

| Condition | Target | Sets | Frames |
| --- | --- | --- | --- |
| [`FixedTemperature`](<https://docs.femforge.io/user-guide/conditions/thermal/#fixedtemperature>) | boundary | `value` \[K\] | [Solid](<https://docs.femforge.io/user-guide/frames/solid/index.md>) |
| [`HeatFlux`](<https://docs.femforge.io/user-guide/conditions/thermal/#heatflux>) | boundary | `value` \[W/m²\] | [Solid](<https://docs.femforge.io/user-guide/frames/solid/index.md>) |
| [`Convection`](<https://docs.femforge.io/user-guide/conditions/thermal/#convection>) | outer shell | `coefficient` \[W/(m²·K)\], `ext_temperature` \[K\] | [Solid](<https://docs.femforge.io/user-guide/frames/solid/index.md>) |
| [`FixedPotential`](<https://docs.femforge.io/user-guide/conditions/current-conduction/#fixedpotential>) | boundary | `value` \[V\] | [Solid](<https://docs.femforge.io/user-guide/frames/solid/index.md>) |

## Body forces

| Condition | Target | Sets | Frames |
| --- | --- | --- | --- |
| [`HeatSource`](<https://docs.femforge.io/user-guide/conditions/thermal/#heatsource>) | body | `power_density` \[W/m³\], `temperature_coefficient` \[1/K\], `reference_temperature` \[K\] | [Solid](<https://docs.femforge.io/user-guide/frames/solid/index.md>) |
| [`JouleHeat`](<https://docs.femforge.io/user-guide/conditions/joule-heating/#jouleheat>) | body | no field | [Solid](<https://docs.femforge.io/user-guide/frames/solid/index.md>) |

### JouleHeat

**Physics** `JOULE_HEATING` · **Target** body · **Section** Body Force · **Kind** `joule_heat` · **API** JouleHeat

Heats a body with the Joule losses of its solved current.

It takes no fields.

Writes: The `Joule Heat` flag.

Put `JouleHeat` on the conductor bodies whose losses heat the model. A conductor without it carries current but stays a passive heat path.