Chevrolet TrailBlazer, Руководство по обслуживанию

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valence ring. Insulators are elements that contain between five and eight valence ring
electrons. Semi-conductors are elements that contain four electrons in their valence ring.
Impedance is something that restricts flow. If you put a number of connections along an
electrical circuit, each connection becomes a source of resistance slowing the flow of
electricity to its final destination. A common analogy would be a coke bottle; if you turn a
coke bottle upside down to empty its contents it takes a longer period of time to do so.
There is resistance within the bottle to empty a large volume of fluid through a low volume
orifice. Now, take the same bottle turned on its side so there is air space present at the
mouth of the bottle while pouring out the fluid. The process takes less time due to low
impedance (less resistance). The resistance we find in an electrical circuit is measured in
Ohms. The resistance of a circuit varies depending on the amount and type of components
used in the circuit. an Ohmmeter is used to measure resistance. Current is applied to the
component from a power source (battery) in the meter. The voltage that returns to the
meter is converter to a resistive value.
The main factors which determine resistance are the material used, the size and cross
section of the wire, the length of the wire and the temperature that these items operate.
Some materials have more resistance than others. Those with high resistance are said to
be insulators. Rubber materials (or rubber-like plastics) are some of the most common
insulators used in vehicles as they have a very high resistance to electricity. Very low
resistance materials are said to be conductors. Copper wire is among the best conductors.
Most automotive wiring is made of copper. Silver is actually a superior conductor to copper
and is used in some relay contacts, but its high cost prohibits its use as common wiring.
Airbag systems commonly use gold plated terminal to ensure that current will readily flow
through the system. Gold, while cost prohibitive, will not react to air and contaminants that
can contribute to unwanted voltage drops.
Larger diameter wires provide more surface area for current flow. The larger the wire size
being used, the less resistance the wire will have. Solid conductors provide less surface
area when compared to stranded conductors. Stranded conductors have the capacity to
carry greater currents when compared to solid conductors of the same gauge (size). This
is because the individual strands of a stranded conductor contribute to greater surface
area. This is why components which use large amounts of electricity have larger wires
supplying current to them. All elements offer some degree of resistance. While copper
wire, as an example, is a conductor, it too has a resistive value. For a given thickness of
wire, the longer the wire, the greater the resistance. The shorter the wire, the less the
resistance. When determining the proper wire for a circuit, both size (gauge) and length
must be considered to design a circuit that can handle the current needed to provide
enough power to the component being powered. With many materials, the higher the
temperature, the greater the resistance (positive temperature coefficient). Some materials
exhibit the opposite trait of lower resistance with higher temperatures (negative
temperature coefficient). These principles are used in many of the sensors on the engine.
As voltage flows through the wiring, these varying properties effect the overall
performance of the electrical system, but the current is what actually does the work.
For any 12 volt, negative ground, electrical system to operate, the electricity must travel in
a complete circuit. This simply means that current (power) from the positive (+) terminal of
the battery must eventually return to the negative (
–) terminal of the battery. Along the
way, this current will travel through wires, fuses, switches and components. If, for any