Differences between a cold and a hot spark plug
Electrons have easier to leave an electrode if the electrode is hot.
In an old electron tube that was used in old radios the electrode in the tube was heated so it was glowing. That enabled electrons to leave the electrode at a lower voltage; the voltage was some 200-300 volt.
It is the same with a spark plug. A hot spark plug will have easier to transmit electrons.
This is how a cold spark plug looks like.
When heated up it looks like this.
The spark time has extended.
The selection of spark plugs shall be according to the manufacturer’s recommendation.
The electron flow is the opposite direction compare to what the current flow according to the definition. That means that electrons flow from the negative pole of a battery towards the positive side. According to the old radio tubes electrons has easier to live a hot electrode compare to a cold.
See more about hot and cold spark plug electrodes in " Neg vs. positive ground systems".