tailieunhanh - Ebook Automobile mechanical and electrical systems: Part 2

(BQ) Part 2 book "Automobile mechanical and electrical systems" has contents: Electrical systems, chassis systems, transmission systems, learning activities, monitoring and instrumentation, manual transmission gearbox. | CH A P TE R 3 Electrical systems Electrical and electronic principles electron proton Electrical fundamentals To understand electricity properly we must start by finding out what it really is. This means we must think very small. The molecule is the smallest part of matter that can be recognized as that particular matter. Subdivision of the molecule results in atoms. The atom is a basic unit of matter and consists of a central nucleus made up of protons and neutrons. Around this nucleus electrons are in orbit, like planets around the sun (Fig. ). The neutron is a very small part of the nucleus. It has an equal positive and negative charge. It is therefore neutral and has no polarity. The proton is another small part of the nucleus. It is positively charged. As the neutron is neutral and the proton is positively charged, this means the nucleus of the atom is positively charged. neutron nucleus Figure Basic representation of an atom The electron is an even smaller part of the atom, and is negatively charged. It is held in orbit around the nucleus by the attraction of a positively charged proton. When atoms are in a balanced state the number of electrons orbiting the nucleus equals the number of protons. The atoms of some materials have electrons which are easily detached from the parent atom and join an adjacent atom. In so doing they move an electron (like polarities repel) from this atom to a third atom and so on through the material. These are called free electrons. Materials are called conductors if the electrons can move easily. However, in some materials it is difficult to move the electrons. These materials are called insulators (Fig. ). If an electrical pressure (voltage) is applied to a conductor, a directional movement of electrons will take place. There are two conditions for electrons to flow: a pressure source, . from a battery or generator, and a complete conducting path for the electrons to move, . wires. An electron flow is .