Introduction: Kelvin's Thunderstorm - Create Lightning From Water and Gravity!

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Did you know that you could recreate thunderstorm lightning in your own home?

It's possible and is really easy to do. Granted, it's not nearly as exciting as a good old fashion thunderstorm, but the effect is still pretty cool and this lightning won't kill you!

The scientific name for this experiment is a water-drop electrostatic generator.

Watch the video for a quick overview, then check out the detailed instructions to see how to build your own! (Scientific explanation is on step 6)

WARNING: This experiment can generate several thousand volts out of thin air, possible injuring or even killing a harmless little gnat or even a fly!

Video overview:



Step 1: Supplies

Here's a list of supplies you will need for this experiment. You can get them all at your local hardware store.


- Garden Hose
- Two buckets - 8 quart or larger are perfect
- Packing Styrofoam
- Hose 'Y' Adapter with flow-control valves
- One foot of 3/4" plastic tubing
- Two 3/4" end caps
- Nylon thread or string
- Wire - any kind of conducting wire works, even alligator leads.
- Two bottomless soup or coffee cans
- A drill with a small bit

Step 2: Prep the Parts

There's a couple of things you'll need to do before putting it all together:

1. Drill holes in the end caps.
This is the most important step. The end goal here is to create several continuous streams of water droplets.

In order to accomplish that, the holes must be properly spaced, otherwise they will join into a solid stream, defeating the purpose.

(This will still work with only one stream of droplets, but the energy buildup time is greatly reduced by having several!)

2. Drill holes in the cans.
The cans will need three holes. Two on top for suspending it from something, and one on the bottom for the metal wire.

Step 3: Prep the Parts - Continued

Now that you have all your holes drilled, it's time to finish the prep work.

1. Attach the wire to the can.
Cut yourself plenty of wire to work with, and make sure it has good contact with the metal of the can.

2. Attach the thread to the can.
Tie one end of the thread to the can. Cut a few feet to ensure there will be enough to suspend it.

Step 4: Put the Pieces Together

Now it's time to put it all together.

1. Connect the y-adapter to the hose.

2. Put the end caps in the plastic tubes.
Be sure they are tight!

3. Attach the tubes to the y-adapters.
I ended up having to use hose clamps to keep them them from slipping off.

Step 5: Put It All Together

Now it's time to put the pieces together.

I used one of those folding ladders to attach the hose to, and to suspend the cans from.

1. Align the cans so they are directly under the tubes.

2. Connect the wire from each can to the opposite bucket.
You can also use the wires to help secure the position of the cans under the plastic tubes.
NOTE: Make sure the wires don't cross or come very close to each other!

3. Move the buckets close together.
This is where the spark will jump. If you can't get them within about 1/2 inch of each other, you can also just attach a couple more pieces of wire to the handles of the bucket and use those for the spark gap.

Step 6: Explanation

So what exactly are we doing with all of this?

Water, like many things, is composed of vast quantities of positive and negative electric charges in perfect balance. As water drips down from the top, the slightly positively-charged water is attracted to the more negative can, and the slightly negative water is attracted to the more positive can.

This water-drop contraption utilizes Electrostatic Induction to generate a voltage difference between the two buckets. The charges then build up in the can connected to the bucket opposite of it - attracting even more charge. This results in a positive feedback loop.

When the voltage difference is high enough (usually a few thousand volts), a spark will jump between the buckets, discharging the voltage.

OK, but how does it start?

During dry conditions, everything near the generator ends up with a tiny electric charge just from being handled. It's the same concept that causes a shock after walking across carpet and touching a grounded object.

Once the water begins flowing, that natural charge is amplified over and over very quickly, resulting in a large imbalance that corrects itself as a spark between the buckets.

For more information about electrostatic induction, refer to these great books from Amazon.com

Electrostatics by Niels Jonassen

Creative Experiments in Electricity

Electrostatic Discharge

Step 7: Turn It On!

Now it's time to turn the electrostatic generator on and begin producing some miniature lightning!

Turn your hose on, and then use the flow control valves on the y adapter to adjust the flow.

The water should come out fairly fast, but it needs to be as droplets and not a continuous stream. A continuous stream won't give the charges a chance to break away from the source, which is grounded.

Ideally, the droplets should begin to form just above the can, before it passes through it. I found that it wasn't very hard to get this working properly without much adjustment.

The water also shouldn't drip on the can, but pass through it instead. A little splashing is normal and doesn't seem to affect the generation of electricity.

Once the water begins flowing, it should only take a few seconds for the first spark to appear. The more individual water droplet streams, the faster and more often you will get sparks!

Watch the video for close-ups of the sparks in action (Fast-forward to 34 seconds to go right to the sparks!):


Step 8: Troubleshooting

If you are not able to get things working as expected, here are some tips for troubleshooting your design:

1. Humidity
If you live in a high humidity environment, don't even bother with this experiment - it won't work. I produced the results you see here with a relative humidity of around 60%.

2. Ground your water source
Your garden hose should be grounded already. If you're having problems getting sparks, grab some extra wire and attach it to the screw of a wall outlet, or carefully attach it to the ground prong of an electrical cord, and then plug it in.

3. Double check your wires from the cans
Are they touching each other?
Are they too close together?

4. Move the buckets closer together.
It's best to move the buckets within a couple of millimeters to start off with, to be sure the generator is working properly. Then you can move them farther and farther apart.