Electrostatics is the study of electric charges at rest.
Electric charge is measured in coulombs (C).
The number of electrons in a charge is calculated by: Q=Ne.
One coulomb of charge contains 6.25×1018 electrons.
Atoms consist of a nucleus (protons and neutrons) and an electron cloud.
Materials and Conductivity
Conductors: Materials like metals that allow free movement of electrons.
Insulators: Materials like plastics and wood that do not allow electron flow; they are easily charged by friction because gained electrons cannot escape easily.
Law of Conservation of Electric Charge: The net amount of electric charge produced in any process is zero; electrons gained by one body equal electrons lost by another.
Methods of Charging
Friction: Rubbing materials together to transfer outermost electrons.
* Positive charge: Rubbing glass or cellulose with silk.
* Negative charge: Rubbing polythene or ebonite with fur.
Conduction: Charging by direct contact between a charged rod and a neutral rod.
Induction: Charging a neutral rod by proximity (not touching) followed by earthing to create a permanent net charge.
Electric Fields
An electric field is a region where a charged object experiences a force from another charge.
Electric field lines represent the direction of force on a positive charge.
Lines point away from positive charges and towards negative charges.
Hazards and Applications
Hazards: Lightning strikes occur when air is ionized by large charge accumulations in clouds, creating a conducting path to the ground.
Pollution Control: Electrostatic Precipitators remove dirt and smoke particles from air by giving them a static charge and attracting them to opposite electrodes.
Xerography: Photocopiers use electrostatics to attract ink to paper.