# Making a needle glow (1000°C) by Battery

So...

is there a way to use a small amount of batterys to get a needle glowing red?

As I understand to heat something up one needs a lot of power which batterys don't supply, so is there a way to efficiently convert small amounts of power in large amounts of heat? Or any circuit to to store energy and then release it in a burst to heat up a small metal object very quick?

The point of this is to making something that looks awesome and dangerous :-)

(rule #32 enjoy the little things)

Not sure about the 1k degrees, but a single car battery will make a screwdriver glow cherry red if suitably mistreated.

what about carbon/graphite rods instead of a needle? mechanical pencil lead makes for a pretty good heating element assuming you find a way to mount it.

so is there a way to efficiently convert small amounts of power in large amounts of heat?

Its a travesty of the laws of physics, but if you figure out how to do it, you’d be a multi-billionaire in a couple of months…

A car battery would almost certainly do what you want, provided you can get a solid enough electrical connection between the needle and the battery, but its a little on the large and heavy side.

so is there a way to efficiently convert small amounts of power in large amounts of heat

It is the conservation of energy physics law that it contravenes. While you can get more voltage at the expense of current or more current at the expense of voltage power is the product of voltage and current, this is measured in watts which is exactly the same units that heat is measured in.

And while you're playing with your new toy, The Car Battery, be sure to wear eye protection, have a fire extinguisher and bucket of water close by, and have a trustworthy friend dial 9-1 (or 9-9)...

http://www.popularmechanics.com/cars/how-to/4213127

http://en.wikipedia.org/wiki/Battery_(electricity) Hazards / Explosion section

http://vimeo.com/8719497

Hmmm no a car battery is definitively too big for a nice place on the window shelf...

Damn those laws of nature :-p

A single 1.5V battery is said to have 2200mAh that would be 2.2Ah which if I'm not mistaken is (theorethically speaking) 1.5V at 2.2A for 1 hour. Or 4.4A 30min. 8.8A for fifteen.. or 132A for one minute --> 198W hehe. (I know no battery can handle this)

Shouldn't it be possible to charge a reasonably sized capacitor bank long enaugh to store such power and then release it within ~5 seconds or so? Accumulated energy over time :-)

Thanks for the links but I don't think I will get a car battery^^

P.s. So there is no inefficent way to produce heat? I thought there were materials which rather radiate heat than anything else...

There's a quote: "A car battery can drive a current of 1000+ Amps for long enough to melt a screwdriver."

But no, you can not get large amounts of power out of tiny batteries.

Note that a modern high-discharge NiCd can make a piece of wire glow red hot, for a relatively short time, even for relatively tiny battery sizes (1/3 AA.) This improvement in batteries is largely responsible for the existence of "electric" RC airplanes and cars; put 100mAH (note: a unit of total energy/power) in the battery, and you can take it out at a rate fast enough to lift its own weight, for a minute or two...

is there a way to use a small amount of batterys to get a needle glowing red?

Have you considered using your batteries to charge up a big(~10,000uF) capacitor and then discharge it through said needle? That would result in an awesome-looking dangerous thing.

It is the conservation of energy physics law that it contravenes.

While you cannot create energy, which is what you are implying, you CAN change the amount of power (energy released/time). You can increase current and thus power with the sacrifice of total time said batteries last for. Batteries discharge a limited amount of current while capacitors don't. If you shorted a small battery with a needle, it probably wouldn't get very warm(ambient air absorbing the heat[energy] as quick as the battery releases it). Whereas a capacitor charged by that battery could potentially evaporate that needle.

A single AA-battery can contain 16,000 Joules of energy. A very generous calculation for the amount of energy required to melt a steel needle weighing 1 gram would be around 1,000 Joules. So my previous statement...

Have you considered using your batteries to charge up a big(~10,000uF)

...isn't true. It would take a 1Farad capacitor charged to 1.5 volts to yield 1,125 Joules.

Batteries discharge a limited amount of current while capacitors don't.

Not strictly true. The current output of a power source is limited by the internal impedance. This tends to be much lower in capacitors than batteries. But a capacitor still has an internal impedance that will limit the current it can supply. However more of a limit than this for capacitors is the current rating, if you discharge (or charge) a capacitor too fast you will physically distort the plates and cause a rupture. So what you are trading off with charging a capacitor is time against impedance.

Not strictly true.

I'll be certain not to exaggerate again in the future.

On a side note: I just realized that I wasn't the first one to suggest a capacitor.. :-/

I’ll be certain not to exaggerate again in the future.

I’ve told you a million times not to exaggerate.

s there a way to use a small amount of batterys to get a needle glowing red?

Like the filament of a small bulb used in a flashlight?

Ok lets put same data together:

Power supply I'd suggest 2 9V-Blocks, parrallel, each 280mAh. Total: 0.56Ah => 5.04Wh

My capacitor has an impedance of 0.08Ohm, capacitance of 1000uF = 0.001F and will be charged with 9V (10Vmaximum rating)

So Ohm's law: U = R * I suggests I can draw: 9V/0.08Ohm = 112.5A

with: C * U = Q 0.009 A*s or Coulomb

I will get a discharge with the duration of: 0.009A*s/112.5A = 0.00000072 seconds

*found an error here, now correct:

Energy of a capacitor: E = 0.5 * U² * C 0.0405J

So in theory I just need to connect 24692 capacitors in parallel :-) (and thats without loss in cables etc.)

Would be great if someone could look over these calculatons and tell me if I'm on the right track!

Cheers!

P.s. the batterys would have the energy of 5.04Wh * 3600 = 18144 Ws = 18144J => ~18 charges

As someone who burnt a hole in a pocket using nothing but two AA cells and a set of keys, you might want to try shorting different batteries.

It's probably quite dangerous, but you could try putting a pin across the terminals of a 9v battery and seeing what happens.

The pin will get hot... but not red glowing (note here that I didn't try this but consider unlikely due to the nature of batterys - also as described above) and then again I want to precisely control when and where the needle begins glowing, speaking of which, my pocket would definately not be on the list :-)

Is 1000°C really a requirement, or are you really just looking for 'glowing red hot'?

If red hot is the goal, then wouldn't a thinner material be a possibility? Seems to me that a small filament should take much less power to get glowing.

Depends on for how long it is required to glow. If you use an old foto flash circuit to charge a sufficiently big capacitor you can even evaporate it.

I did something like this. 400uF at 300V will store 24J. This is enough to evaporate some part of your needle.

The interesting question though is: what exactly is your usecase?

Udo