Understanding the functions of your Geo spark plug wires can help you diagnose your car's combustion system when problems arise. Your Geo spark plug wires carry the high-voltage electrical current that has been produced by the ignition coil to the terminal of the spark plug. Once at the plug, the electricity travels to the other end of the plug, and jumps a gap between electrodes to produce the 'spark' that ignites the fuel mixture. The spark is created when an insulator breaks down and allows a rapid discharge of electrons across it. A quick review of your basic physics can also help: According to the first law of physics: moving a magnet past coiled wires causes current to flow in the wire, since the coiled wire is a complete circuit. According to the second law of physics: current that flows in coiled wires causes a magnetic field to surround the wires. To handle that current flow, Geo spark plug wires are made of a conductive core and insulation, which is made of silicone rubber. The core is usually a carbon impregnated fiber or wire; they can be made of anything from nylon to Kevlar. That conducting core is bent over at the wire end and the boot metal is crimped over the core/insulation of Geo spark plug wire. Some premium wires will be designed with copper or stainless steel wire wound around the carbon core to reduce resistance. Take a quick review of all the name-brand Geo spark plug manufacturers offered here and compare their materials and features.