Triboelectric effects are used to define the signs of charges. A glass rod rubbed with silk has a positive charge and an ebonite rod rubbed with cat's fur is negatively charged. The components should be kept in a disiccator to keep them dry. There are many materials from which one can obtain charges due to triboelectric effects.
|Electroscope and the electrostatics box containing an acrylic rod
|a piece of silk
|ebonite rod and a piece of cat's fur