Machines and living things convert stored energy to motion and heat. Energy from the Sun can be changed into other forms of energy. Electricity comes from several sources, but all of them can be traced back to energy from the Sun. Electricity is carried through wires to places where it is used, like our homes. Here it is changed into heat, light, motion and other forms. Machines use energy to produce motion and heat. Fuel is the energy source, which a car, plane, train or a boat uses to produce motion. Have you touched the hood of a car after a long trip? As the engine converts the fuel into motion, heat is also produced. Humans and animals convert food energy into the energy of motion and heat, when you eat a turkey sandwich, the energy contained in it gives you the energy, you need to walk, play football or run across the schoolyard. The body also uses the food to produce thermal energy to keep you warm, when you play outside on a cold day, you gradually feel warm because the energy of motion produces heat. So it is better to move around on cold days than to stand still.