* Convection: Hot air rises. The heating elements in an oven are typically located at the bottom, which heats the air below. This hot air rises, creating a convection current within the oven. The hot air at the top of the oven then cools and falls back down, creating a cycle. However, this cycle isn't perfectly efficient, and the hot air at the bottom of the oven doesn't always fully mix with the cooler air at the top.
* Radiation: Oven elements also emit infrared radiation, which is a form of heat energy. This radiation travels in straight lines and is absorbed by surfaces. The bottom of the oven is closer to the heating elements, so it receives a higher dose of radiation. The top of the oven receives less radiation, as the heat has to travel further and some of it is absorbed by the air and the oven walls.
* Conduction: The oven itself, including the racks and walls, absorbs heat from the heating elements. This heat is then conducted to the food inside the oven. This conduction is more significant at the bottom of the oven due to the closer proximity to the heating elements.
Therefore, the temperature at the bottom of an oven is higher due to a combination of:
* More direct heat from the elements: both through radiation and conduction.
* Less mixing with cooler air: the convection currents are less effective at the bottom, leaving hotter air closer to the heating elements.
This is why it's important to rotate food during baking, as the bottom can easily overcook while the top remains underdone.
