I know this question will expose my ignorance in so many different levels, but, do electric sparks ignite flammable liquids because it is hot or because it is electric (you know, like ionizing…I don’t know what I’m talking about)? Can anyone understand the question?
I understand that ordinary sparks, like one gets from rubbing flint vigorously causes fire because of the heat. I’m just wondering if electric sparks carry an added advantage in that it’s electric.
It’s the heat. Electric arcs heat the air around them, in the same way that current flow can heat a conductor (as in a light bulb) - in other words via resistance converting electrical energy to thermal energy. The temperature of the arc is dependant primarily upon the current flowing through it.
Flint and Steel or Electric Sparks consist of tiny bits of incandescent (visibly hot) metal which is/are used to ignite tender or to light a combustible mixture of inflammable vapor and oxygen (air).
Electric sparks are not incandescent metal.
When I walk across the carpet on these dry winter days and touch my wife while she’s sitting on the couch, a visible spark can leap from me to her. If there’s glowing metal flying from my skin to hers, we’ve got problems.
:smack:
Thanks for pointing out that I was not explicit.
An electric spark from two wires will eject bits of molten copper (or wire metal) which can ignite flamable vapors.
Rarely. And only for a very high-current arc. But, as I pointed out in my previous post, the primary cause of ignition is due to the resistive heating of the ionized air the arc is flowing through. This is just as true for lightning as it is for a static spark from your cat.
How do you think the spark plugs in a car engine work? It ain’t by ejecting bits of molten metal. If they did eject bits of molten metal, you’d be changing your spark plugs every few hundred yards.
Fire is a very complex chemical reaction. On reading the question, my first impulse was to simply say “its the heat,” as the three requisites for a fire are heat, fuel, and oxygen. However, let’s think about it: free radicals are an important part of the fire cycle. Extinguishers like halogenated hydrocarbons work by scavenging free radicals (as well as other mechanisms). An electric arc is accompanied by the generation of ozone, produced by formation of free-radical oxygen. Perhaps, this *could * play a role in initiating a fire.
just thinking out loud here…
I was actually thinking along the same lines. I was wondering if that plays some role. When I get hit by an electric spark coming from a disposable lighter, the sensation I feel is not one of heat…but you could say the same thing for the fling type sparks…oh well…