Magnesium!

[Nick1911]

If one were to pass a large current across a piece of magnesium ribbon (think "short circuit across a magnesium fuse"), would it ignite before melting and breaking the circuit?

I think it would, due to magnesiums auto-ignition temperature of 883F, and melting point of 1202F.

Anyone tried this or seen it done?
 

[AJ Dual]

I suspect the difference would be academic at best.

If it ignited, the extra heat from combustion would be melting the ribbon a bit as it burned, if it melted, it would probably auto-ignite.

My grandfather had an envelope of zirconium shavings he'd retrieve a sample from and burn for me now and agian. 

[charby]

I wonder how many amps that would take?

[slugcatcher]

I wonder how many amps that would take?

It depends on the gauge of the wire.

[Nick1911]

It depends on the gauge of the wire.

Exactly!

Really, it's not amperage we're concerned with - it's watts of power dissipated per unit of material.

[Rudy Kohn]

It's possible the magnesium would oxidize without burning before you reach the auto-ignition point if you go too slowly.
Many metals will do this.  Gold, somewhat obviously, will not, and can be made to glow cherry-red before the ribbon breaks due to points melting.

[seeker_two]

Anyone tried this or seen it done?
 

Care to share why you want to do this?......



....before Homeland Security shows up at your door.... 

 

[Headless Thompson Gunner]

You'd probably have better luck coating the magnesium wire with a substance that ignites at a lower temperature and burns hot enough to ignite the magnesium.

Or you could just buy some thing magnesium wire and try it.  A car battery ought to provide enough juice to either prove or disprove the concept.

[AJ Dual]

You'd probably have better luck coating the magnesium wire with a substance that ignites at a lower temperature and burns hot enough to ignite the magnesium.

Like Dry Ice? 

http://www.youtube.com/watch?v=WoBp2m035OA

[never_retreat]

Just hitch it up between the leads of a welder and crank up the amps till it lights.

[Physics]

If one were to pass a large current across a piece of magnesium ribbon (think "short circuit across a magnesium fuse"), would it ignite before melting and breaking the circuit?

I think it would, due to magnesiums auto-ignition temperature of 883F, and melting point of 1202F.

Anyone tried this or seen it done?
 

I imagine it would depend on how quickly you ramped up.  If you slowly ramped it up then yeah, I'd say it would ignite first but for a quick (ie: instantaneous) turn on, I imagine it would do both.  Either way, I think it's igniting. 

I've done a lot of thermal evaporation in my semiconductor research.  I did a research project creating organic transistors and one of the steps involved putting powdered pentacene into a tungsten crucible and ramping up the current slowly, until the crucible was glowing orange. I don't remember the amperage offhand, it's in my notebook, which is with the PI for that project.   

I haven't worked with Mg, though I imagine I could have some fun with it.  :D

[dogmush]

It will ignite.

I'm not sure of the exact sequence, weather it melted and lit, ot lit and melted, but you get a satisfying bright white flame, that will ignite a mixture of Aluminum and Iron Oxide, if the magnesium happens to be sitting in it. 

I used a thin strip I had cut off one of those camping firestarters, Jumper cables, and a 750CCA batt.

I also won $20, because my IT guy bet me that whatever I did to my old harddrives left data on them he could get.  Not so much.

[slugcatcher]

I also won $20, because my IT guy bet me that whatever I did to my old harddrives left data on them he could get.  Not so much.

It's hard to pull data from slag. Got an "after" pic?