Electricity

Electricity is the movement of electrons from one atom to another.

Background Knowledge Needed to Understand Electricity

Atoms - the basic unit of a chemical element.

Proton - a subatomic particle, symbol p , with a positive electric charge. Protons and neutrons form the nucleus of an atom

Neutron - a subatomic particle, symbol n , with no net electric charge and a mass slightly larger than that of a proton. Protons and neutrons together constitute the nucleus of an atom.

Electron - a subatomic particle, symbol e , with a negative elementary electric charge. Electrons are not found in the nucleus, rather they are constantly moving around the nucleus. Eletrons have a much smaller mass than protons or neutrons (approximately 1/1835).

Nucleus - the positively charged central core of an atom, consisting of protons and neutrons and containing nearly all its mass.

Electron Cloud - an informal term in physics. It is used to describe where electrons are when they go around the nucleus of an atom. The electron cloud model is different from the older Bohr atomic model by Niels Bohr.

Electron Orbitals - In quantum mechanics, an atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom. This function can be used to calculate the probability of finding any electron of an atom in any specific region around the atom's nucleus.

These drawings represent the structure of an atom but are not accurate. The nucleus would be much smaller compared to the size of the electron cloud and electrons do not revolve around the nucleus in neat orbits, but rather move in much less predictable paths.

These drawings are more accurate but harder to understand representations of an atom. For our discussion of electronics you can ignore these if they confuse you.

The Bohr Model provides a very useful drawing of the atom for our discussion of electricity.

Bohr Model - depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus—similar in structure to the Solar System

Valance Shell - the outermost shell of an atom, which contains the electrons most likely be separated from the atom. This is also where extra electrons could be added to the atom. Each shell can contain only a fixed number of electrons: The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the n^th shell can in principle hold up to 2(n²) electrons.

Valance Electron - an electron that, when associated with an atom, exist in the outer most shell of the electron cloud.

These are three examples of drawings based on the Bohr model of the structure of the atom. In these drawing you can easily see the valance shell (outer most ring) and how many electrons are in it.

Ion - an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

Positive Ion - an atom that has lost one or more electrons, leaving it with more protons than electrons, so that it has an overall positive charge.

Negative Ion - an atom that has gained one or more electrons so that it has an overall negative charge.

Electrical Conductivity of Materials

Conductors

Insulators

Semiconductors

Superconductors

Types of Electricity

Static Electricity

Direct Current

Alternating Current