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Roget's Spiral

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I have to make a working model to demonstrate Roget's Spiral experiment. The apparatus originally used included mercury. But since it applies to all electrolytes ,I would just pour common salt in water and use it. Would it produce spark or not?

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Roget's spiral ---> coil, corkscrew, curlicue, gyration, gyre,helix, screw, whorl

Sorry - I'll get my coat and leave

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I don't see why it wouldn't work. Along the same lines I've been meaning to build a Faraday motor using salt water instead of mercury.

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One more thing, I am using two cells of 1.5V each. Would they be enough for it? What should be the thickness of coil for it?

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One more thing, I am using two cells of 1.5V each. Would they be enough for it? What should be the thickness of coil for it?

 

The motor I already built used a single battery; the resistance of the wire will give you an indication of the current that will flow. It will be lower than V=IR, because there is also an inductance that adds to the impedance, but the overall behavior will depend on the configuration (e.g. pitch) and the mechanical properties of the coil.

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I think this is one of those things that should work in theory but might be difficult to get working in practice due to the relatively high resistance of salt water when compared to mercury. I think,for example, that the resistivity of sea water is about 5 million times that of mercury. I don't know what the resistance of a pool of saturated salt solution would be but I can see that very high voltages might have to be used to get enough current to make either device operate (IMO). Anyway, best of luck and worth a try!

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I think this is one of those things that should work in theory but might be difficult to get working in practice due to the relatively high resistance of salt water when compared to mercury. I think,for example, that the resistivity of sea water is about 5 million times that of mercury. I don't know what the resistance of a pool of saturated salt solution would be but I can see that very high voltages might have to be used to get enough current to make either device operate (IMO). Anyway, best of luck and worth a try!

 

So, I would be making an attempt with two cells of 1.5V each. If it didn't work, I would plug the wires in the switchboard.

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I have finally done the experiment. I used the electricity which comes to our home (220V). It worked with ease. I saw a spark, one end of wire made a small hole in the bowl(steel). But I couldn't saw the spring contract and relax as it was instantaneous. But since the spark is produced, I succeed in it.

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I have finally done the experiment. I used the electricity which comes to our home (220V). It worked with ease. I saw a spark, one end of wire made a small hole in the bowl(steel). But I couldn't saw the spring contract and relax as it was instantaneous. But since the spark is produced, I succeed in it.

 

Glad you are still alive !! it's very unwise to experiment with mains voltages so I suspect a bit of a wind up! Also the device is designed to work with a DC supply although the coil should tighten regardless of current direction.

Edited by TonyMcC

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Glad you are still alive !! it's very unwise to experiment with mains voltages so I suspect a bit of a wind up! Also the device is designed to work with a DC supply although the coil should tighten regardless of current direction.

 

My mom kept warning me. I thought I should take risk. After all science is fun and risk. But the wire had insulation.

Still, the spark was so sparkling that I got scared and dropped the spring in the NaCl. There wasn't a spark again! For attraction between the coil, they should be in different media than electrolyte.

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Glad you are still alive !! it's very unwise to experiment with mains voltages so I suspect a bit of a wind up! Also the device is designed to work with a DC supply although the coil should tighten regardless of current direction.

 

Are you really sure if it would work with AC too?

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Are you really sure if it would work with AC too?

 

I've never made one or applied AC to one so my answer is an opinion. All that seems necessary for the turns of the helix to be attracted to each other is that current flows around the turns so that adjacent turns carry current in the same direction. This will happen regardless of the direction of current passing through the coil. It seems to me that applying AC will shorten the distance between the turns in a pulsating fashion and this should make the device work. I neglect the effect of the coils inductance because the frequency is relatively low and there is no iron core to consider. I suppose if the individual tugs of attraction are small and the ball is heavy you might only see the coil vibrating. I repeat this is something I have never tried but my answer seems to agree with theory.

Edited by TonyMcC

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I want to make roget's spiral for my 12th cbse project.. can someone just guide me how to start with..?? plzz..

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I want to make roget's spiral for my 12th cbse project.. can someone just guide me how to start with..?? plzz..

Two years back, I did it and now I know I did it wrong. Salt water, using AC source both were wrong choices that wouldn't allow you to observe the spring motion. The good way is to use merury, decent DC batteries. I think you know the idea how the spiral works?

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Before using mercury, can anyone please explain to me why the bottom contact can't just be a piece of metal?

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John, when the spring would contract, metal base would prevent it from doing so as per Lenz's law. So the periodic motion of spring might not be clearly visible? Hg is also a metal though.

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If I hang a spring from a stand so that the lower end dangles in free air then raise a metal plate under it until it just touches the bottom of the spring, how does it prevent it from contracting?

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In that case, metal would support contraction. As you raise metal, flux through it increases and it tends to oppose the factor increasing the flux.This case is different from what is intended to be shown in Roget's spiral.

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I don't think I have made myself clear.

When the metal plate just connects with the spiral, stop raising it.

 

Then, the spiral will contract due to the magnetic field it produces, which will break the circuit so the coil will relax again and re connect to the plate and the cycle repeats.

 

In essence, what's special about mercury?

Why not use copper?

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When the circuit breaks and the coil tries to come down, copper would provide an upward force so that it can resist increase in flux. Since copper is better conductor, the effect might be more. I suspect that's why mercury is quoted in books.

Am I understanding you correctly?

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