In this topic you will learn about using energy from many different sources.

Chemical reactions in a battery produce electrons. When electrons in a circuit pass through a light bulb, they give up some of their energy to a very thin wire in the bulb called the filament. The filament gets hot enough to glow and give off light.

Energy is stored in batteries. We refer to the energy stored in an object or material as potential energy. Any object that is moving has kinetic energy. An electric motor changes electrical energy into useful kinetic energy.

Energy is a measure of how much work something can produce. To scientists work means moving matter around with forces. Energy is not matter—it is the ability to move matter around.

We also describe energy by its source or how it is carried. Chemical energy is stored in links between atoms. Mechanical energy moves gears, axles, and wheels. Thermal energy is carried by heat and radiant energy is carried by light.

Two ways heat can flow are conduction and convection. In conduction, the energy moves from a hot object that comes into contact with a cooler object but the materials remain in place. Convection means the movement of energy by the flow of matter from place to place.

Heat can also move—by radiation. Radiation is the movement of energy in the form of waves that can travel through empty space. Any warm object always gives off infrared, or heat, radiation.

The wet cell battery in a car contains sulfuric acid solution. A wet cell battery contains a liquid solution that produces the electric current. Flashlight batteries do not have a liquid inside so they are dry cell batteries. A dry cell battery uses "dry chemicals" to produce an electric current.