Saturday Science: Electric Dough
Chances are you’ve probably played with Play-Doh or some modeling dough or clay at some point in your life. It’s fun, it comes in all sorts of colors, and you can make whatever you want. With a little work, you can even use Play-Doh to conduct electricity! Don’t worry; nobody is going to get shocked. We’ll be using small batteries to keep things safe. To do this project you can use regular Play-Doh, but if you don’t have any, you can follow the recipe we’ll give you. You also have to make a second kind of dough, a special “insulating dough” that won’t conduct electricity, before you can start plugging lights and motors into your Play-Doh. Have a grown-up help you out in the kitchen for a great rainy day activity!
To make this a little easier, we’ll split it into three sections: how to make the conductive dough, how to make the insulating dough, and how to use them to make electrical circuits.
- 1 cup of water
- 1 ½ cups of flour
- ¼ cup of salt
- 3 Tbsp cream of tartar
- 1 Tbsp vegetable oil
- Food coloring
- Medium-sized pot
- Cooking spoon
- Cutting board
- Mix the water salt, cream of tartar, vegetable oil, and 1 cup of your flour in your pot. Add a few drops of whatever food coloring you want.
- Put the pot on your stove over medium heat and stir it continuously. Your dough mixture will eventually start to boil and get chunky. Keep stirring until it starts to form a ball in the middle of the pot.
- Take the ball out with your spoon. Dust your cutting board with some flour and place the dough down on top of it. It will be very hot so let it sit for a few minutes until it’s cool enough to touch.
- When it’s cool, knead the dough while slowly adding the leftover ½ cup of flour until it gets to the right consistency.
- 1 ½ cups of flour
- ½ cup sugar
- 3 Tbsp vegetable oil
- ¼ - ½ cup distilled water (It’s really important to use distilled water and not tap water.)
- Mix the sugar, 1 cup of the flour, and the oil together in a large bowl.
- Add 1 Tbsp of distilled water and knead it into the mixture. Repeat this until it becomes moist and doughy. You may not use all of your water.
- Take the mixture out of the bowl and slowly knead it, adding your leftover flour, until it becomes firm.
- Conductive dough
- Insulating dough
- AA batteries
- A AA battery pack with wires (leads) coming out
- LEDs, tiny motors, fans, or whatever you can think of. Make a visit to Radio Shack and go crazy!
- Flatten out two pieces of conductive dough and one piece of insulating dough, all roughly the same size.
- Make a sandwich with your insulating dough in the middle. We added food coloring to the conductive dough, so it’s easier to tell the two types apart.
- The battery pack should have two leads, one black, and one red. Make sure that the plastic is off the ends of the leads and a little metal is showing. Don’t touch the metal of the two leads together or touch it with your hands.
- Put your batteries into your battery pack.
- Poke the metal from the red lead into one of the pieces of conductive dough and then poke the metal from the black lead into the other piece.
- To start, take a small LED. Notice how it has two different metal wires poking out from its bottom. Just like you did with the battery pack, put one into one piece of conductive dough and one into the other. If everything is connected correctly, it’ll light up!
- Any LED, motor, fan, or other cool little electronic gizmo that has two wires can be plugged in in the same way. Try other things out!
- Once you have the basics down, get creative with your clay. As long as there’s insulating clay in between two pieces of conductive clay, the sky’s the limit! Do you want to make a unicorn with a glowing LED for a horn? Go for it!
A lot of things are happening here. First of all, we have two different types of dough. The “conductive dough,” that electricity can move through, and the “insulating dough” that it can’t. They’re both dough, so how come one is friendly to electricity and the other isn’t? It’s all in the ingredients we chose.
Your conductive dough has three ingredients in it that help it to conduct electricity: the salt, the cream of tartar, and the regular old tap water. When salt and cream of tartar mix with other substances, they break apart into tiny little pieces called ions. Salt breaks into ions of sodium and chlorine and cream of tartar release ions of potassium. These ions, mixed into the dough, allow the electricity to flow through it. Think of it as the electricity is jumping from ion to ion inside the dough. The tap water, like most water, also has ions in it.
Your insulating dough (“insulating” means that energy, like electricity, can’t move through something) doesn’t have any of those ingredients. Flour doesn’t break into ions, and neither does sugar. The most important ingredient, though, is the distilled water. Distilled water is very, very pure. It doesn’t have any ions in it at all. If you tried to drink some while you were making your dough, you might have noticed that it tastes funny, way different from the water we usually drink. The ions in normal water give it the taste we’re used to. Since your insulating dough has no ions in it, the electricity can’t flow through it.
But why do we need it in the first place? Why not just get a big glob of conductive dough and plug the battery pack and the LED into it? Wouldn’t that work? You can give it a try if you want, but you probably won’t have a lot of success.
Now we’re out of the realm of chemistry and into the realm of electrical engineering. To get the kinds of results that we like from our electricity, it has to flow in what’s called a circuit. Think of a circuit like a loop of electricity (“circuit” and “circle” have the same root word. It has to go out one of the wires on the battery pack, to the thing we want to power up, and then back into the battery pack through the other wire. When it’s flowing in this complete loop, we have a closed circuit and the LED lights or the fan spins or whatever we want to happen happens (if there’s enough energy.)
If we just plugged the battery pack and the LED into one big clump of conductive dough the electricity would flow, all right, right through that dough and back into the battery pack without ever touching the LED. It would create what we call a short circuit because the electricity jumped back to the battery before it got to the thing we wanted it to power up. We need to give the electricity two paths to flow down: one toward the LED and one away from the LED back to the batteries. That’s why we need the insulating dough in the middle: to make sure no electricity flows between the two clumps of conductive dough and creates a short circuit.
To see this kind of short circuit in action you can do a little experiment: once you have a working circuit with the two kinds of dough, take a little piece of conductive dough and make a bridge out of it. Connect it to both pieces of your conductive dough. What happens to the object you have plugged in?