# Electrostatics

Electrostatics is the study of electric charges at rest. The forces between electric charges are described by Coulomb’s Law. Electrostatics are used in devices such as laser printers and photocopiers.

# What is Electrostatics?

Electrostatics is a discipline of physics concerned with the study of electric charges at rest. Since the ancient Greeks (and possibly earlier), humans have known that some materials can attract lightweight objects when rubbed. For example, amber rubbed on cat hair will attract small feathers. This, and other electrostatic phenomena, are caused by the forces that electric charges exert on each other.

The electrostatically generated forces we encounter on a daily basis may seem small, but these forces can be dramatically stronger than other forces such as gravity. The electromagnetic force between an electron and a proton in a hydrogen atom is approximately 36 orders of magnitude larger than the gravitational force acting between the two particles!

The forces between electric charges are described by Coulomb’s law. It is also interesting to note that the word “electricity” is derived from the Greek word for amber.

## Coulomb’s Law

Coulomb’s law is the mathematical description of electric force between charged items. Static electricity is a well-known electric phenomenon involving the transmission of charged particles from one body to another. For example, when two insulators are rubbed together in dry air, the items accumulate equal and opposite charges, and an attraction force arises between them. The object that loses electrons becomes positively charged, whereas the object that gains electrons becomes negatively charged. The force is caused by the attraction of opposite-sign charges.

## Applications of Electrostatics

• Van de Graaff Generators are remarkable gadgets designed to display the high voltages caused by static electricity. They are capable of generating huge static charges and commonly used in science classrooms to demonstrate lightning and make students’ hair stand on end.
• Xerography, as applied in photocopier machines, uses electrostatic charges on a light-sensitive photoreceptor to attract and transfer powdered toner particles onto paper. The toner is then fixed in place, typically through the application of heat, thereby making copies of the original document.
• Inkjet printers and electrostatic painting use electrostatics to control the deposition of a thin mist of microscopic, electrostatically charged ink droplets.
• Prevention of electrostatic build-up is also important in both electronics assembly and agriculture. Many electronics components can be damaged by electrostatic discharge, and electrostatic build-up in grain silos has been known to cause spontaneous explosions.