Electrostatic Meters: Electrostatics
Projector Electroscope
PIRA Class: 5A22.35*

Purpose
To demonstrate a means of relative measure of net charge.

Description
By direct contact or charging by induction, observe the relative charge of a charged object. Needle will register according to the relative measure of net charge present, whether positive or negative.
- Charging by induction: Placing the object near to the electroscope, the electroscope  knob will acquire the opposite charge of the object at hand. Needle will then have the same charge as the object. (Object's net charge is not changed during this process.) The closer the object is brought to the knob, the greater the separation of charge within electroscope, the greater the register of the needle. Move the object away from electroscope and electroscope charges will redistribute 'evenly' about, and needle will return to original position.
- Charging by contact: By bring the object in contact with the   knob of the electroscope, charge can then transfer from object to the electroscope. Needle register will depend on the amount of charge transferred. Remove object from electroscope, and electroscope will remain charged.
NOTE: If irregularities are observed in the interactions of the charged objects, it is recommended that all synthetic, including black carts, materials involved be rinsed off with water or wiped down with a wet cloth.

Equipment
Projector Electroscope, charged object
Support Equipment
Overhead Projector