Basic Differential Electroscope or Electrometer
An electrometer is an electrical instrument for measuring electric charge or electrical potential difference. The electroscope is an early scientific instrument used to detect the presence of electric charge on a body. It detects charge by the movement of a test object due to the Coulomb electrostatic force on it. The amount of charge on an object is proportional to its voltage.
Included: 1 Electrometer as shown in picture.
Not Included: Requires a 9V battery.