Fire

[cwes99_03]

High current DC. AC would cause an alternating magnetic field, though this too might be interesting, largely it would not be visable as it cycles at 60 hz from the outlet.

 

The reason you saw the flame move was that you were moving the air near the flame.

 

What no one has commented on is that the visable part of the flame isn't the entire part, there is a vast area in the infra-red spectrum there too. This might be more notably affected by a strong electromagnet.

 

By the way, to do this experiment you want to set up a stationary electromagnet, light a candle near it. Then ramp up the DC current (ramping up the voltage will cause the current to be ramped up as you have a fixed resistance in the wire.) Test this to see if you can find a measureable effect dependend upon the current (which is directly related to the strength of the magnetic field).

[cwes99_03]

Oh and BTW, the fire exhausts its oxygen supply by creating a pressure gradient around the flame nexus. If the flame were to grow too large, the oxygen couldn't get near the source of the fuel. It seems to me to be a self regulatory process.

[Jay-qu]

well, lets talk specifics now, if im really gonna do this then im gonna do it properly! so lets discuss:

-solinoid material

-type of wire

-no. of turns of wire

 

and anything else that anyone comes up with.

 

I know that the number of turns can increase the magnetic field but its also going to increase the resistance and hence drop the current...

[CraigD]

well, lets talk specifics now…

A possible alternative to winding your own electromagnet is to use one from a transformer – if you’re like me, you likely have some unused 110VAC-to-DC block power transformers around.

 

Since (I’ve read) these things usually rectify the AC current into DC on the low-voltage side, you’ll need to acquire and install a diode to the AC side, before it enters the transformer. Unless you’re lucky enough to have a transformer with a cord running between it and the AC outlet, you’ll likely need to add a cord, so that you have a place to wire in the diode.

 

The core of the transformer is probably a double ring – to get a gap with a strong magnetic field, you’ll need to remove at least some of the plastic covering, and cut a notch in one side of the exposed steel or iron ring, wide enough for the flame to pass through.

 

For the flame, I think the sort of butane lighter with a long tube sold for lighting candles and grills would work best. Unless you can get one with a non-magnetic tube, you’ll likely need to work out a way to clamp it so that the magnet doesn’t grab the tube.

 

If you decide to building your own electromagnet, there appear to be a lot of good sites with formulae and practical details if you google “electromagnet”, such as this one. Ceramic insulated wire can be had at retail places like Radio Shack, and a C-shaped core could be bent out of steel rod.

 

It goes without saying to be careful around 110V electric power, and be certain not to touch anything live while it’s plugged in. Also note that I’ve never tried this myself (beyond the nail-and-1.5V battery), so treat my recommendations with healthy skepticism.

[Jay-qu]

A possible alternative to winding your own electromagnet is to use one from a transformer – if you’re like me, you likely have some unused 110VAC-to-DC block power transformers around.

 

Since (I’ve read) these things usually rectify the AC current into DC on the low-voltage side, you’ll need to acquire and install a diode to the AC side, before it enters the transformer. Unless you’re lucky enough to have a transformer with a cord running between it and the AC outlet, you’ll likely need to add a cord, so that you have a place to wire in the diode.

 

The core of the transformer is probably a double ring – to get a gap with a strong magnetic field, you’ll need to remove at least some of the plastic covering, and cut a notch in one side of the exposed steel or iron ring, wide enough for the flame to pass through.

 

For the flame, I think the sort of butane lighter with a long tube sold for lighting candles and grills would work best. Unless you can get one with a non-magnetic tube, you’ll likely need to work out a way to clamp it so that the magnet doesn’t grab the tube.

 

It goes without saying to be careful around 110V electric power, and be certain not to touch anything live while it’s plugged in. Also note that I’ve never tried this myself (beyond the nail-and-1.5V battery), so treat my recommendations with healthy skepticism.

 

but the the whole principle of a transformer is that it needs a changing flux, wont the diode stop this from working? or does the half wave still do this...

[thomas_e_lafferty]

I've been thinking about this for a few minutes, and an answer isn't coming to me. Why does fire have a well-defined outline? Any ideas?

-Will

 

There is one other thing to consider when determining the "outline" of a flame:

what instrument is doing the detection of the boundary?

 

My guess is that you are referring to the human eye, and as I am sure you are well aware, the human eye has some significant limitations. Therefore, while we may in fact perceive the boundary of the flame as continuous and well defined, it may in fact be something else.

 

Some of the limits that the eye imposes are as follows:

1. lack of "freeze frame"

2. macroscopic view

3. inability to see beyond light in either direction (longer or shorter wavelengths)

 

Were you to use an infrared detector, or some other instrument of detection, say x-ray, you would see an entirely different image, though some of the boundary phenomenon may still be present.

 

I'm not sure that I have answered your question; however, I felt it was important to establish what instrumentation was being used.

[CraigD]

but the the whole principle of a transformer is that it needs a changing flux, wont the diode stop this from working? or does the half wave still do this...

I believe the half wave would still produce moving magnetic field, so induce a current in the output coil.

 

However, remember, we don't care if the transformer still works. We'd rather it didn't even have an output coil. All we want is its electromagnet function. If we could feed pure, smooth DC, into the input coil, we'd be happiest, but unless you've a nice DC power supply around, or a mess of batteries and the daring to wire them in series, that'd take a bit more work.

 

:hyper: Maybe someone here or on the larger internet knows how to build a DC power supply, and can help out. But, since the object is just to get a visible effect on the flame, not necessarly a neat, smooth one, I'm hoping the DC half-wave will work.