What Are the Different Types of Electroscope?

Electroscopes use mechanical means to help detect electric charges in substances. Electroscopes have been created by various inventors over the years, using different materials or providing modifications in design. However, just three major types of electroscopes remain popular today for scientific use and classroom demonstrations--the pith ball, golf leaf and spin. Electroscopes with scales that permit specific measurements are known as electrometers or voltmeters.

Pith Ball

• A pith ball electroscope contains a small lightweight ball of a non-conductive substance suspended by a silk thread attached to an insulated stand. Objects are brought close to the ball and if they're charged, they will attract the ball. Pith balls become charged when they've touched a charged object, allowing scientists to also test the polarity of objects based on the known ball charge in keeping with the laws of polarization. The electroscope receives its name from the original substance of the lightweight ball, pith.

Gold Leaf

• The gold leaf electroscope provides greater sensitivity than the earlier pith ball model. To imagine this type of electroscope, picture a conductive base with a bell-shaped jar--usually of glass--over it. Suspended from the inside of the jar is a brass rod, with two thin strips of gold leaf attached to the end. On top of the jar, in contact with the brass rod, lies a small metal plate. Individuals use the gold leaf electroscope by touching an item to the metal plate on top of the jar. Charged items will cause the gold leaves to spread apart. More strongly charged items may cause the same effect from a short distance without contact.

Spin

• The third type of electroscope is the spin electroscope. The spin electroscope is frequently used to demonstrate static electricity, making it a staple in many science classrooms. The spin electroscope consists of a non-conductive plate with a metal rod sticking out of the center. This rod has a perpendicular rod attached to its top, which in turn has two angled ends. The spin electroscope will spin when approached with a charged item such as a friction rod. The spin electroscope is the most basic of all the different electroscope types.