Electrostatics experiments and demonstrations

Electrostatics is the branch of physics concerned with electric charges at rest and the forces between them. Classroom experiments and demonstrations make these otherwise invisible effects visible, showing how objects become charged, how charges attract or repel, and how charge moves through or stays on materials. The underlying idea is that matter contains positive and negative charges; rubbing certain materials together transfers some charge from one to the other, leaving each object with a net charge.

A familiar starting point is the triboelectric effect: rubbing a plastic rod with cloth or fur lets it pick up small pieces of paper, or makes a hair stand on end. Such demonstrations illustrate the basic rule that like charges repel and unlike charges attract. The electroscope, a device in which thin metal leaves spread apart when charged, gives a simple visible measure of the presence and sign of charge. Charging by friction, by contact and by induction can each be shown with everyday materials.

Larger demonstrations use machines that accumulate substantial charge. A Van de Graaff generator builds up high voltage on a metal sphere, dramatically raising a volunteer's hair or producing visible sparks, while a Leyden jar or other capacitor stores charge for later discharge. These experiments connect to wider physics topics, since the same principles of charge, electric fields and potential underlie electric circuits and lightning. Working with static charge also calls for care, because high voltages can give an uncomfortable shock even when the stored energy is small.

Frequently asked questions

How does rubbing objects together create static electricity?

Rubbing transfers charge from one material to the other, leaving one with extra negative charge and the other positive, a process called the triboelectric effect.

What does an electroscope show?

Its thin metal leaves spread apart when the device holds an electric charge, giving a simple visible indication that an object is charged.

Why does a Van de Graaff generator make hair stand up?

It charges a person's body to a high voltage, so each hair carries the same sign of charge and the strands repel one another.