Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

Whenever my three year old son plays on his trampoline, it doesn't take very long for him to start building up a significant amount of static electricity. His hair stands on end (which is quite amusing), but when I help him down we both get a nasty static shock (which is not amusing).

He finds the shock upsetting, and I'm concerned that it will discourage him from enjoying his trampoline.

How can I prevent the build-up?

One suggestion I have seen on a parenting forum is to ground the trampoline frame with a cable and a metal stake. However my understanding is that this would enable him to discharge by touching the frame (rather than me), but it would not prevent the static occurring in the first place.

If it's relevant, it's this trampoline and is on a grass lawn. My son bounces in his socks, no shoes. In case of link rot, it is an 8ft trampoline with a net enclosure.

share|improve this question
    
That's surprising - never observed this with a very similar trampoline and my 3-year-old (now 4) niece+nephew twins. It must be a combination of materials everywhere, including the shoes and clothes. Moreover, the humidity has to be very low in your case. If it's high, e.g. 80% - you may help it by spraying water around - the static electricity buildup will decrease 10-fold or more. –  Luboš Motl Apr 12 '13 at 9:46
1  
It doesn't happen to me when I bounce on it - I don't know what's special about him! Have now clarified in my question that he wears socks when bouncing. –  Sir Crispalot Apr 12 '13 at 9:50
    
Possible duplicates: physics.stackexchange.com/q/4180/2451 and links therein. –  Qmechanic Nov 13 '13 at 2:16

5 Answers 5

up vote 6 down vote accepted

Four possibilities come to mind, in decreasing order of feasibility:

  1. Is barefoot an option? I'm willing to bet it will significantly mitigate the buildup of charge.

  2. The two of you only experience a shock on contact because you are at different electric potentials. If you can't keep him at your potential, why not try to join his? Before helping him down, perhaps you could rub your (sock- or sneaker-) clad shoes on a thick rug kept near the trampoline. Then make sure the first surface he touches is a mediocre conductor (the ground may very well be sufficient). Unless he has an extreme buildup of charge, he probably won't notice the slow discharge through his feet this way.

  3. In labs containing sensitive electronic equipment, people often wear grounded wrist straps. If you are always connected to ground, you can't build up much of a charge. Of course, this could hamper more extravagant displays of acrobatics.

  4. In case all else fails, here's a last, entirely untested suggestion. You could try to either ground or insulate the trampoline surface itself. For instance, take some very thin wire (as in, thickness of a strand of hair, so it can't be felt through the trampoline) and run it under the trampoline. Basically, affix a grid of wire to the underside (leaving slack to allow for the trampoline surface to deform) and ground it. If charge has a harder time building up on the surface, it has a harder time building up on your son. Alternatively, engage in materials experimentation. There may very well be a spray-on coating that can be applied to the top of the trampoline surface that happens to reduce the chances electrons will be knocked free of it.

share|improve this answer
    
Thanks for the great answer - hopefully it will be dry enough this weekend to try your suggestions! –  Sir Crispalot Apr 12 '13 at 15:31

Dryer sheets rubbed on you before you both get on there, works great for us!

share|improve this answer
    
Yes indeed. Dryer sheets contain a cationic surfactant that is good (if not 100% effective) at preventing static buildup. –  John Rennie Dec 21 '13 at 19:30

The charge is produced by rubbing between the socks (or feet) and the bed of the trampoline, and by cloths rubbing on skin as he jumps. This is called the triboelectric effect. Grounding the frame of the trampoline will not make much difference because the bed is not normally a conductor unless wet.

The solution is to change the clothes he is wearing, especially the socks. For safety reasons it is not recommended to bounce barefoot and it wont help much because dry skin can just as easily generate a charge. Better solution is to wear cotton which does not generate much charge. Other materials can be tried but synthetics like nylon are the worst.

Different materials have a tendency to gain positive or negative charges. Cotton is one of the few non-conducting materials that does not gain much charge. You could also try wool. Fabrics such as nylon will build a positive charge when rubbed. The worst case is if the bed is made of (or coated with) a material that gains a negative charge e.g. rubber. If you really want to be scientific about it and can find out what the bed is made of, you could look up a triboloectric series which lists materials in order of the charge they build up from positive to negative. Materials that are closely matched in the series will not build much static when rubbed together see e.g. http://www.trifield.com/content/tribo-electric-series/

Don't neglect the possibility that most of the charge is coming from his clothes rubbing on skin or other clothes, so try a cotton t-shirt etc.

share|improve this answer

Get a grounding rod and bang it into the ground? Get 2 ground clips and 1 meter of 6mm grounding wire. Link 1 clip to the leg of the trampoline and then the other clip to the grounding rod.

share|improve this answer

It might be the specific combination of sock material and trampoline material that's to blame: some combinations will transfer a charge, some won't. Socks of a different material might mitigate this; there are a number of "anti-static socks" on the market, but I'm not sure any of them come in three-year-old sizes.

Has he tried trampolining barefoot?

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.