English Across the Curriculum
A battery has liquid or paste in it that helps it produce electric charges. The flat end of the battery has a negative charge and the end with the bump has a positive charge.
When you link a wire between both ends a current flows. When the current passes through a light bulb electric energy is converted into light.
The chemicals in the battery keep the ends charged and the battery going. As times passes, the chemical becomes weaker and weaker and the battery cannot produce any more energy.