Bending Water with a Plastic Comb

Yes, yes, I seem to have an affinity towards bending stuff, specifically wet stuff. Last time I bent a laser beam using water, and this time I’m going to magically bend water using a plastic comb.

Science magic! Okay, well, it’s not quite magic, it’s science magic, which means it has (as always) a perfectly good explanation to it. But – can you guess it?


This is a very straight forward demonstration about static electricity, and it is working so well, that it really is fun to do anywhere with a faucet (and a plastic comb..).

What Do You Need?

  • A plastic comb or a nylon balloon.
  • Dry hair.
  • Dry environment (humidity is baaaad)
  • A very thin flow of water (about 1 cm thick, or for all you metric-deniers, about 1/16th of an inch).

What’s Going On?

Well, the plastic comb is made of molecules (as is every other matter) that have electrons floating around them. Electrons have a negative charge, and just like a polarized magnet, they are repelled by other negative charges.

When I comb my (dry!) hair with the plastic comb, it collects electrons from the individual strands of hair to itself. About 10 strokes should be enough to make the charge strong enough for the demonstration. The electrons move from my hair strands to the comb and, therefore, lose negative charge. The individual hairs become positive (because they have lost negative charge), the comb becomes negative (because it gained negative charges, in the form of electrons).

The molecules in the water stream are neutral – they have both positive and negative charges, and all their electrons nicely floating around wherever they are supposed to be. When I move the (now negatively charged) comb next to the water stream, the electrons that are closer to the comb are being repelled away. The molecules that are closer to the comb, therefore, become positive, and away from the comb there is more negative charge (more electrons).

The side of the water flow that is closer to the comb is now positively charged, and the comb is negatively charged. Positive and Negative attract one another, and that concept allows the water flow to bend towards the comb.

Voila! instant science magic!

Practical Applications

Static electricity exists in nature, as you may well have noticed in a hot, dry day, trying to open a metal door knob and heard a tiny Bzzzz, followed by an inconvenient sting. Our body exchanges electrons with the surroundings all the time, gathering up and discharging static electricity. But there are more applications and phenomena that are attributed to static electricity:

  • Electrostatic Percipitator: This invention is used to clean the air from other particles by inducing electrostatic charge. It’s quite useful, specifically for power plants or big industrial facilities.
  • Xerography: this is a photocopying technique developed in the late 1930s. It distributes a uniform electrostatic charge on a surface of a drum. The image is then lit through (so wherever there is color, the surface remains unlit) on a grid on top of the charged drum. The light dissipates the charge, so the grid remains charged only where the image is printed. Then, carrier particles are mixed through the drum and “soaked” into the paper – so they “stick” where the charge exists, and therefore duplicate the image.

More References

14 comments
dkye
dkye

Would the temperature of the water vary with how well the water bends?

mooeypoo
mooeypoo moderator

@dkye Off the top of my head, I would doubt that the temperature would have an effect -- especially with the range of temperature that can come out of a faucet at home. But I would say that this is a great idea for a home experiment, and you should try it!


The only challenge here is to try and make the variables the same from each experiment. Try to make sure the stream remains stable in various temperatures, and then you can measure (a) how close do you need to get the comb to the stream to make it bend, and (b) how far it bends. See if there's a noticeable difference -- but make sure to test multiple times.


If you do the experiment, I'd love to hear your results :)

sciencemaniac
sciencemaniac

could u explain further on why ur hair frizzed when u combed it?

Jamaican Stone
Jamaican Stone

I remember doing this electrostatic experiment when I was in primary school. It was really fun at that time. Your post just remind me of my sweet child of mine.

Abby
Abby

Actually protons (positive) can't move, only electrons (negative) can. We did this experiment in school and the water moved away from the negatively charged comb because the electrons moving away from the comb.

Mark
Mark

Very nice demonstration. Just a suggestion if I may; I wouldn't use the word "prove", it gives the wrong idea about science, which is not about "proving" things, but about giving plausible theoretical explanations to concepts. If we convince kids that we are "prooving" things we'll promote the idea that science is absolute truth which - as any scientist should know - it most enphatically isn't. Thanks for listening.

S
S

Hi, very nice demonstration.

We did this in school although it probably was a failure because we only had too minutes.

Plus none of us were willing to brush our hair with the same comb everyone else used.

Oh well!

~S~

James
James

Hi, I found your blog on this new directory of WordPress Blogs at blackhatbootcamp.com/listofwordpressblogs. I dont know how your blog came up, must have been a typo, i duno. Anyways, I just clicked it and here I am. Your blog looks good. Have a nice day. James.

Silvio
Silvio

Is the levitation of objects possible through proton electrons and photon energy possible?

if so, can you demonstrate an example??

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