Common Ground: Flames and Electricity

The interplay between an arc welder and a candle flame.

Power. It’s a word with a multitude of meanings. When using it you might be referring to a physical unit of work per unit time, a mathematical exponent or the ability to exert influence over a given entity.

Hell, you could be making a joke about the losing streak of the Adelaide football team.

In the current age of technology, however, by far the most common use of the word is as a measure of electrical current.  Electricity powers our homes, keeps us warm, provides light for our streets and cooks our meals.  It has been perhaps the sole driving force behind the advances in computation, medicine, refrigeration, industrial production, space exploration, transportation and just about every other technological step forward you care to name over the past hundred years.

Similarly to electricity, there is another naturally occurring phenomenon that once lifted us to a new level of defensive and supportive capability as a species. Fire; the harnessing of which kept us warm, provided light and cooked our meals in much the same way as the use of electricity does now.

So what do an electric current and a flame have in common? The answer is in the electrons.

Transferral of charge is the crucial common element linking these two energy sources. The difference is that electricity involves the movement of negatively charged electrons, whereas a flame consists of the dispersal of both positive and negative ions. So we can sort of think of fire as the mirror image of electricity; the medium of one is shifting in the other and vice versa.

This relationship between electricity and fire makes for a couple of intriguing characteristics when they’re brought together. We all know that magnetic and electric fields are closely interconnected, but did you know that you can influence the behaviour of a blaze with a strong enough magnet?

The following video by ‘Veritasium’ demonstrates beautifully the ionic nature of a flame, identifying that the negative and positive components of both the fire and the remaining smoke are attracted to opposite ends of a magnetic field.

The video also rather dramatically highlights another fascinating aspect of the electricity-fire relationship, which is that the ions in the flame cause that region of space to be more electrically conductive than the surrounding (non-ionized) air.

Wait, fire can conduct electricity? Woah.

A Volcanic Thunderstorm

6 Responses to “Common Ground: Flames and Electricity”

  1. RuthBlair says:

    It’s why you must never ever wrap an electrical lead around a metal bar in the theatre or you turn the entire rig into a magnet. wrap enough leads (like so many you wouldn’t be doing it for any other reason than the laughs) and wrap an actor in an appropriate metal, turn the power on and voom, flying actor. Please do not try this, ever. there are fly rigs for surprise flights across stage.
    The theory being that electric current produces a magnetic field. when you wrap a whole lot of them together, their powers combine to make a giant magnet. This is how you get elctro magnets, like the ones to lift cars. Turn the power on, magnetic field created, move the car, turn the power off and the car falls.

  2. reimer says:

    I have to admit, I felt slightly embarrassed when I read “We all know that magnetic and electric fields are closely interconnected”. Ahem.

    But still, this article is really interesting. Again, forgive my ignorance, but if you hypothetically had a huge bonfire going and a thunderstorm struck, would you be morelikely to be struck by lightning?

  3. Ryan Hodgman says:

    @Oliver Whitton: I had heard notions about putting fires out with electric fields thrown around, but I think that’s patently ridiculous. You’re liable to just start more fires. What is interesting though is that lightning tends to strike more often in bushfires, due to the increased conductivity of the surrounding atmosphere. Perhaps fire could be used as a method to control (dare I say, harness?) discharges of lightning. Mostly I just find it interesting to think about.

    @Erik: Thanks for pointing that out! I’m sure the number presented in the attached video just happened to be what voltage they were using at the time, not taking into account the electrical resistance of the materials involved. The important point to note is that a flame reduces the resistance of the gap between the plates as compared to air at room temperature, implying the presence of ionized particles.

  4. Erik J. says:

    One detail is slightly wrong,
    “It takes about 20,000V to spark through 1cm of the air”
    Well, it depends mostly on the ESR of the electric source. If you have a certain ultra capacitor, it can contain about 220V, because of it’s extremely low ESR it can spark at about half a cm of air.

  5. Oliver Whitton says:

    Pretty cool. I’m going to ask the dreaded question: What practical applications can we get out of this? I don’t think it really matters of course, it’s a really cool thing to know about fire and what it actually is but I love a good practical application no matter how esoteric.

  6. Ruth BLAIR says:

    i think that picture of the volcano fire thunderstorm is pretty much the coolest photo ever. Love this article, it’s awesome!!