h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Is this for real? And if so, how/why does that work?

http://uk.youtube.com/watch?v=DsG-0lU6FbY


Sorry, for those on slow internet, it's a demo of running a small light or dc motor using two candles, two nails, two leads, and a magnet.

no, it isn't. The magnetising bit is carp - that wouldn't work as the nails would not be magnetised by that action.
Also note the hand under the table and that the light shines and the motor spins. And when they turn off. And the light turns off after the first candle is blown out.

And, not inconsequentially, the fact he's claiming that lighting a candle can induce an electrical current!!! Not only that, but lighting the left candle induces one electrical potential and lighting the other induces the opposite electrical potential without any change in materials or techniques. Come on....

Probably just a magic trick, but if you're curious then why not try it out?

I couldn't see any way that it could work, but then I'm not a scientist

If it's a trick how does he make the motor go even when he keeps all the circuit visible?

The nails must go all the way through the candles and are hooked onto a real electric circuit of some kind through wires hidden by the candles.
You can just about see that he's flickeing a switch underneath the table just under the right hand candle.

Besides, rubbing a magnet on nails like that is going to do just about naff all to the nails.
Iron is not a permanent magnet, you can only magentise it by putting continous current through it.

Iron isn't a permanent magnet?

Hmmm, yes it just might be in fact. But nevertheless, rubbing a magnet against a nail like that is going to have about as much effect at magnetising it permanently as any of us are likely to have in attempting to pull a 50 wagon train with our teeth.

...or at least giving it enough energy to drive a motor or light a bulb that brightly.

Orcus : Post 7

"But nevertheless, rubbing a magnet against a nail like that is going to have about as much effect at magnetising it permanently as any of us are likely to have in attempting to pull a 50 wagon train with our teeth."

I can pull a train that long with my teeth. The only real problem I have in doing it is lining up that many wagons without some kid running off with a couple of the middle ones.

Cheers Orcus, I agree with the overall point

And why would you use *two* big candles to light one dim bulb? Light is light...

This has to be a hoax. Even if you could somehow induce an electrical current with a candle, there is no way that the electrons can flow if the circuit is not complete. Hoax.

And burning the wicks at the top won't do anything to heat the nails below, if that's the supposed purpose...

I was wondering whether lighting the candles could cause the air to ionise around the candles, thus completing the circuit

Also, I agree that attempting to magnetise the nails using 'that action' is not ideal, it may well work. (Normally, one uses one pole of a magnet to stroke along the nail in one direction, lifting the magnet clear after each stroke nd returning to the start point to repeat the action. In this way the magnetic domains are persuaded to line up.

But I'd have thought that the amount of current that could be induced to flow by either of the deficiencies above would be too low to light a bulb or run a motor.

Ref the iron not being a permanent magnet, an iron nail or a steel paperclip that has been magnetised in some way can retain its magnetism for a considerable time. This is the case even if you make it into an electromagnet by placing it inside a coil of wire.

This is sufficiently intriguing for me to want to try it out Hope it's not April 1st

I looked again at this, quite carefully and I agree with the obs. mentioned above about the hand reaching under the table. Also, the candle didn't light properly the first time around and yet the bulb shone brightly - even with the candle extinguished momentarily. Also, when the candle flickered back into life, there was no correlation between the brightness of the bulb and that of the candle. HOAX!

(But I'm still tempted to try it. GULLIBUUULLL!)

spoiler

how to do it

put 2 contacts (nails) through the desk, under the candles and conect to power supply and switch

insert a conductor(metal spike) into base of candle

insert nails in candle to contact conductor, place candles down so as to compleate cuircit with the contacts

light the candles and flip the switch

"I was wondering whether lighting the candles could cause the air to ionise around the candles, thus completing the circuit?"

No, it takes an electric field of tens of thousands of volts per inch to actually strip atoms of their electrons and ionize the air i.e. a lightning bolt or vandegraff generator.

How about this one. A battery made from wood ash:

http://www.youtube.com/watch?v=5h1tQn4Qyjc

Is that for real?

That one is definitely for real. A simple alkaline cell battery. All the chemistry at the beginning is genuine and workable.

B