Range Rover County LWB (LH) V8-4.2L (1993)
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Cruise Control Module: Diagnostic Aids
Electrical Theory
THE KEY TO UNDERSTANDING ELECTRICITY, ELECTRICAL CIRCUITS AND TO INTELLIGENT TROUBLESHOOTING IS A
THOROUGH KNOWLEDGE OF ELECTRICAL FUNDAMENTALS. THE FOLLOWING INFORMATION IS DESIGNED TO REVIEW
THESE FUNDAMENTALS.
ELECTRICITY
Electricity is an invisible force which behaves according to definite rules and produces predictable results and effects. Although we have learned to
produce, store, use and measure electricity, no one knows just what electricity is. In recent years, scientists have developed the Electron Theory to
explain the nature of electricity. It explains more thoroughly than any other theory, the behavior of electricity and magnetism.
ELECTRON THEORY FUNDAMENTALS
1. Everything consists of matter.
2. Matter is made up of molecules.
3. A molecule is made up of 2 or more atoms.
4. Atoms contain protons, neutrons, and electrons.
The nucleus of an atom has a positive electrical charge (+). An orbiting electron has a negative electrical charge (-). An electrically balanced atom has an
equal number of positively charged protons in the nucleus and negatively charged orbiting electrons.
All atoms except hydrogen have a third component called a neutron. The neutron is a neutral particle, neither positive nor negative. Neutrons are
clustered at the center with the protons but do not affect the balance of charges of the atom.
BOUND AND FREE ELECTRONS
The electrons in an atom revolve in one or more orbits around the core. The number of electrons in the outer orbit affects the ability of the atom to
combine with other atoms and its ability to conduct electricity. Atoms tend to complete their outer rings; that is, to acquire as many electrons in the outer
ring as possible. Although an atom can not have more electrons than it has protons, it can share electrons in its outer ring with other atoms. This is how
atoms join themselves together to form molecules. Electrons in the inner orbits of an atom are closer to the positively charged nucleus and are strongly
attached to it. These electrons are called bound electrons. Electrons in the outer orbit are farther from the nucleus and less strongly attracted. These are
called free electrons.
ELECTRON FLOW
When atoms share electrons with one another, the positive and negative charges of each atom become unbalanced. As an electron moves from the outer
ring of one atom into the outer ring of another atom, the first atom becomes positively charged because the protons momentarily outnumber the electrons.
The protons instantly seek to attract another electron from another atom to rebalance the charge. This unbalancing and rebalancing of charges takes place
very quickly (less than a microsecond), and the movement of free electrons from one atom to another is called electron flow, or electric current flow.
This does not mean that any single electron travels the full length of a conductor. Instead, free electrons move from atom to atom and this movement
results in the transmission of an electrical impulse from one end of a conductor to the other.
CONVENTIONAL THEORY OF CURRENT FLOW VS. ELECTRON THEORY
The Electron Theory states that current flows from "-" to "+". However, in automotive electrical systems we use the Conventional Theory of Current
Flow: Current flows from the "+" terminal of the battery through the circuit and back to the "-" terminal of the battery. The Conventional Theory works
well for automotive usage because modern automobiles ground the battery terminal.
MAGNETISM FUNDAMENTALS