Today’s ovens come in two basic types: electric or gas. An electric oven uses large coiled wires inside that heat up in order to cook the food. There are two sets of these coils, one on the top and one on the bottom. These heating element heat up when electricity is sent to them. The bottom coil of wires is the one that cooks the food when you bake. The dial on the oven controls an internal thermostat. When you turn it to set the temperature, a copper wire that leads to the cooking area is alerted to the temperature that you want. This wire serves as the temperature gauge, and it sends signals to the thermostat to turn on and off based on the temperature inside the oven. The top heating coil is the broiler. This coil will heat to high temperatures very quickly. It does not have a temperature control like the coil on the bottom. It will heat to its highest possible temperature and stay there until you turn it off.
A gas oven works in a similar fashion, but uses a flame instead of an electric coil to heat the food. The bottom of the oven has a burner that is activated when the temperature knob is turned. It also has a copper wire that serves as the temperature gauge. When the desired temperature is reached, the burner shuts off. When the temperature begins to dip, it turns the flame on again. The flame is fueled by LPG gas and is ignited by an internal lighter as soon as the gas begins to mix with air. Most gas ovens also have a flame at the top of the cooking area that serves as a broiler.
Most modern ovens are self-cleaning ovens. When the self-cleaning feature is used, the thermostat on the oven heats both the broiler and the baking heating elements as high as possible. This chars any debris that is in the oven, and after several hours the oven shuts off and the charred ash can be removed. The oven will have a lock that must be set to use this feature, as the internal temperatures get dangerously high while it is cleaning.