The arc from the Isuzu Spark Plug is what ignites the air and fuel mixture in the combustion chamber of your engine. This arc is from the core of the spark plug in its center to the electrode that protrudes from the end.
To create this powerful arc at the end of the Isuzu spark plug an electrical charge is sent to it through the plug wire to the top end of the plug. This charge of electricity then jumps to the other end of the spark plug through the center ceramic section of it. This ceramic center is hollow and non conductive so the electrical impulse will not dissipate or be redirected by any means when supplying power to your Isuzu engine.
This ceramic section is a vital part of the spark plug and care should be taken when handling it so no damage will occur to it before one is installed in your Isuzu. If a plug is dropped, it could damage the ceramic hollow shell in the plug causing it to crack. This would break the vacuum on the interior of the plug preventing the electrical charge from jumping between points in the plug. A plug in this condition would be considered faulty and in need of replacement.
Another important factor about a spark plug is the gap between to center core of it and the electrode. This distance has to be within specifications for the maximum potential of the arc to be realized in your Isuzu engine. If the gap is too great or too small, then the arc will be weak and not fully ignite the air and fuel mixture in the combustion chamber of your engine robbing you of both performance and mileage.