1. 3.2 Convection In an electric oven, food is cooked using heating elements which heat the air around the food. An electric ovenExample 2 layer of mineral wool shiny metal foil oven wall heating element inside oven

2. 3.2 Convection When air around the heating elements is heated, it expands and becomes less dense. Then the air rises. Cool air in the oven is denser. It sinks and takes the place of the rising air. A convection current is therefore formed. The air in the oven is heated up and in turn heats up the food. (a) Explain how heat is transferred from the heating elements to the food by convection.

3. 3.2 Convection (b) Some ovens have a fan inside. Explain the function of this fan. The fan is used to mix the hot air and the cool air so that the air is heated up evenly. (c) The oven wall contains a layer of mineral wool. Explain how this can reduce the rate of heat transfer. The wool traps air which is a poor conductor. It also prevents convection to occur inside the oven wall.