Talk:Kelvin water dropper

Lacking description?

How are the rings made negative or positive in the first place? They must have a charge to begin with to start the system off- otherwise there would be no difference between the water droplets on either side and nothing would happen. Either way either the description is lacking- it needs to be added that the rings need to be intially charged or it needs to be stated how the rings become initially positive and negative on their own 81.179.187.5 20:10, 23 September 2007 (UTC)

I'm no expert, but this appears to work by amplifying the difference. So provided they don't start out at the exactly same charge they will migrate away from each other. --RadioElectric 21:15, 4 December 2007 (UTC)

RadioElectric is correct. One of the cans is already randomly positive or negative, and to put it simply, the Kelvin Water Dropper mearly amplifies such an effect. By the way, someone should verify the thing about droplets being better than continuous streams. I am not sure if it is true at all, but it is definitely not true for the video. I'm not going to do it myself because I'm lazy, but any volunteers? --Armaetin (talk) 08:15, 13 January 2008 (UTC)

A continuous stream wouldn't work because it would effectively electrically connect the two buckets and thus equalise the charge. —Preceding unsigned comment added by 98.248.33.53 (talk) 02:19, 22 December 2009 (UTC)

As the operation of the generator depends upon the separation of the charges, the droplets keep the separation as they break away and carry their charge with them. A continuous stream of a conductive liquid allows a discharge and neutralizing path, as the previous entry states. However non conductive liquids such as fuels, and similar liquids will carry their charges with the flow and accumulate and build to dangerous levels in the containers they fill unless they are properly bonded and earth grounded.1bobwhite (talk) 18:01, 20 May 2010 (UTC)

Even a stream of water that separates droplets just before the bucket would have almost the same problem, as the drops would have very little charge on them when breaking away. Jokem (talk) 14:34, 6 February 2014 (UTC)

I don't understand your objection. I believe the device is designed so the stream breaks into drops either above or inside the induction electrode. The 1867 drawing, which may be Kelvin's original, shows the stream breaking into drops in about the center of the electrode. As long as it separates into drops above the electrode center, the electric field in the solid stream will be in the correct direction to separate the ions. --Chetvorno^TALK 15:05, 6 February 2014 (UTC)

I think it can break up into drops even below the induction electrode and still work. Most efficient would be to do this right in the middle, I think. Jokem (talk) 06:05, 30 January 2015 (UTC)

Even if there were no initial charge difference between the buckets, the equilibrium would be unstable and possibly sensitive to any quantum or classical (chaotic) fluctuations. Note in particular that the random finite number of ions in a droplet may often not even be mathematically able to represent the exact average charge of the source, leading to a tiny difference when the droplet lands in one of the buckets. Even unamplified differences will eventually add up to a normally distributed total difference, which can then be amplified. Elias (talk) 09:32, 6 March 2023 (UTC)

Link to video doenst work

"This is a private video. If you have been sent this video, please make sure you accept the sender's friend request." —Preceding unsigned comment added by 86.134.244.191 (talk) 21:42, 26 April 2008 (UTC)

efficiency

How much power does this thing generate? Can it be used to generate a stream of power instead of lightning bolts? What is a good efficiency comparison to say... a turbine generator? —Preceding unsigned comment added by 67.168.139.24 (talk) 23:57, 15 December 2008 (UTC)

is there a solid state implementation

can it be implemented as solid state? (i.e. without water with electrons and magnets..., something without moving parts) —Preceding unsigned comment added by 84.109.234.81 (talk) 05:57, 21 February 2010 (UTC)

The device converts the motion of water driven by gravity into electric potential. Elias (talk) 09:58, 6 March 2023 (UTC)

principles of operation

It is my humble opinion that the reference to hydroelectric power in the last paragraph does not agree with the topic of electrostatic generators and the production of static charges. 1bobwhite (talk) 17:31, 20 May 2010 (UTC)

Indeed. "As with other forms of hydroelectric power, the energy here ultimately comes from the gravitational energy released by letting the water drops fall." Were this true, it would seem that increasing one or more of the vertical dimensions would increase the power produced. Yet, it is far from obvious how this could happen. Surely it is the proximity of the rings to the water source that allows them to attract water with opposite charge. And it is difficult to see how the distance to the bucket could affect the power. If nothing else, there's some explaining to do in the last paragraph. JKeck (talk) 03:06, 8 February 2011 (UTC)

On further reflection, I realized that, while it's the electrostatic force that pulls the charged water to the oppositely charged ring, it's gravity that has to pull the water to the like-charged bucket (and keeps the charges "together"). While the energy wording is of course correct, phrasing it in terms of force may make for a clearer explanation. JKeck (talk) 02:34, 9 February 2011 (UTC)

The origin of the energy that can be extracted/discharged is from the gravitational potential of the elevated water. A higher water drop would put more energy into the system, but there would be no guarantee that more energy would be harvested. The article indeed states that the device is not an efficient generator, that much energy is wasted to heat as drops/droplets simply splash into the reservoirs. I can't avoid pondering how the design could be optimized for other applications than physics demonstration, though. Ideally, one would want the electrical field to brake the droplets to a soft landing. Also, regarding the undesirable occurrences of droplet-ring discharge, shouldn't it be possible to separate the droplets from the rings mechanically, by extending the pipes through the rings? The microscopic version referred to near the end of the article reportedly achieves an efficiency of 48%, which is not that bad. Elias (talk) 09:47, 6 March 2023 (UTC)

chemical reaction

So what is happening anyway? From what i can tell, OH- and H3O+ naturally exists in the container. The electric field guides the ions to the positive and negative container. But then, how does is the potential increased? There are no free electrons or something... 130.89.234.108 (talk) 16:37, 4 July 2010 (UTC)

Potential increases due to the work of gravity on the drops separating charges. This is not a chemical reaction. Graeme Bartlett (talk) 00:52, 6 July 2010 (UTC)

But where does the charge in the drops come from? 130.89.233.218 (talk) 07:30, 7 July 2010 (UTC)

Appears randomly, as the drops separate from the dripper, or by absorbing an ion from the air. A cosmic ray could knock off a few electrons. Once a difference exists the machine amplifies it. That's why article speaks of 'positive feedback' the slightest imbalance in charge is amplified; just like a bullhorn squeeling, or a laser begining to generate light.

71.139.165.48 (talk) 08:02, 30 November 2012 (UTC)Graeme Bartlett (talk) 11:01, 7 July 2010 (UTC)

Ok, now how does it amplify? I ask because as water doesn't conduct, explaining it by electrostatic induction seems odd. 130.89.167.48 (talk) 20:46, 16 July 2010 (UTC)

But a moving drop of water with a charge on it does conduct. Water does have enough conductance to balance the charge out in time scales under a millisecond. See Water (properties)#Electrical conductivity. Graeme Bartlett (talk) 21:52, 16 July 2010 (UTC)

The mentioned article only argues in favor of ion conduction. —Preceding unsigned comment added by 130.89.232.35 (talk) 19:33, 28 July 2010 (UTC)

And if the tubes acting as conduits for the water are made of metal, most of the conduction is done that way. Also, ordinary tap water has trace amounts of ions in it which are enough to significantly increase the electrical conductivity of the water. Jokem (talk) 09:12, 26 January 2015 (UTC)

It may be interesting to experiment with using distilled water, and salt water, to see if there are differences as compared with tap water. Also, all parts of the device should be supported by good insulators that are shielded so as not to become wet. The device always uses only two cylinders, but I imagine that better results might be gained by using some higher multiple of 2 number of cylinders, with the drops alternating in charge as they drop through; this is worth a try. David Spector (talk) 00:54, 21 April 2016 (UTC)

Drippers connected together

The 'detailed article' in the links says to electrically bond the two (or more I guess) drippers. Maybe this should be in the main article too. 71.139.165.48 (talk) 08:03, 30 November 2012 (UTC)

This part seems to contradict what you are saying, but doesn't immediately make sense to me: "Investigations of the Kelvin Electrostatic Generator under various controlled conditions showed that it operated with tap water, distilled water (non-deionised) and a saturated solution of NaCl.[10] It was also found that the generator worked well even if the two liquid streams originate from different electrically insulated reservoirs. A model was proposed in which the electric charge results from the separation of the positive aqueous hydrogen ion and the negative aqueous hydroxyl ion as the water droplets form." Elias (talk) 08:56, 6 March 2023 (UTC)

Mistake: charge resides in the water

The article states, "Otherwise, the container-end of each wire must dip into the water. In the latter case, the charge resides on the surface of the water, not outside of the containers."

This is incorrect. As charge is deposited by the wires into the water, it almost instantly moves away from the wire and the water to the outer surface of both metal containers. The repulsion of each unit of charge pushes the charge as far away from the like charges as possible. This is why, if a static electricity generator includes metal spheres, the electric potential will be highest on the outside of the spheres, and is why, if there is a sharp point, the potential will be greatest at the tip. The location of a spark, if any, shows where the potential is greatest.

If someone has time to find reliable references for these facts, the article's mistake should be corrected. David Spector (talk) 00:43, 21 April 2016 (UTC)

In the current version, "Otherwise," refers to the case where the containers are not made of metal. Elias (talk) 09:54, 6 March 2023 (UTC)

Length and diameter of the rings, overall dimensions, scalability

I am missing references to the dimensions of the device in relation to the efficiency, plus some absolute values regarding the generated power (i.e. achievable voltage, current, the amount of water required to "generate" a specific amount of energy, as well as the simplest question: How long does it take until a electric spark can be seen in a standard lab setup?). How does the length and diameter of the rings effect the operation, what about the speed of the drops or streams? 147.161.138.200 (talk) 01:48, 28 December 2023 (UTC)

Some of this data may be in the scientific papers cited in the References section of the article, but they are behind paywalls. Unlike for example the Van de Graaff generator, this device was never used as a practical generator of power, it was just a laboratory experiment illustrating electrostatics for students, so there may not be answers to most of your questions. Educational manuals that instruct science teachers how to perform the experiment might have additional information. --Chetvorno^TALK 13:54, 28 December 2023 (UTC)