Charge

Charge is a property of an object that can be positive or negative.  Charge describes a deficiency in or surplus of electrons on the object. The electron is the basic unit, or quantum of charge.  The charge of an electron is -1.6 x 10-19 C. Atoms normally have neutral charge because the proton has the opposite charge as the electron and most atoms have equal numbers of protons and electrons. Objects become charged when electrons are transferred from one object to another. Removing electrons makes an object have a positive charge; adding electrons makes an object have a negative charge. Total charge is conserved, meaning the total number of electrons and protons does not change. There are four basic processes for charging: friction, conduction, grounding and induction. Three of these processes involve the removal or addition of electrons from an object – friction, conduction and grounding. Induction involves a temporary polarization of charge caused by a change in the distribution of electrons in an object.

Different devices utilize different methods of electron transfer. An electroscope detects charge, using induction, conduction and the repulsive effects of like charges to show when charge is present. A Van de Graaff generator moves electrons from the Earth and allows them to accumulate on the dome. Friction, conduction and grounding are used within the Van de Graaff generator. By understanding that charge is conserved and how objects become charged you can understand the operation of different technological devices.