Light the Holidays Lights with Playdough

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Can playdough conduct electricity? Can you built an electrical circuits using playdough rather than wires?

 

You’ll need:

Conductive playdough:
2 cups flour
¼ cup salt
3 tbsp cream of tartar
1 tbsp cooking oil
1 cup water
Food colouring

Insulating playdough:

2 cups flour
½ cup sugar
3 tbsp cooking oil
½ cup distilled water

For the circuits:

LED lights, at least 2 (can be found in hardware stores)
4 AA batteries (1.5V each)
Battery holder for 4 batteries with wires (can be found in hardware stores)
Optional: motor and buzzer

Make the playdoughs:

Mix all the ingredients in a large bowl.
Knead and add flour or water if needed.
Note: the insulating dough is gooey and much less pleasant than the conducting dough.

Test different kind of circuits:

Insert the batteries into the battery holder

Circuit A

Make 2 small balls from the conductive playdough.
Connect each ball to one wire of the battery holder.
Stick the LED in the playdough, one leg in each ball. Make sure the balls do not touch each other.
Did the LED lit? If not, try to reverse its legs in the playdough.
Now make a contact between the balls. What happened to the light?

Circuit B

Exchange the conductive playdough with the insulating one.
Did the LED lit? What about if you reverse its legs in the playdough?

Circuit C

Make 2 small balls of conductive playdough and 1 from the insulating dough.
Set the insulating ball in the middle between the conductive ones.
Connect one wire to each ball and stick the LED legs in the conductive balls.
Did the LED lit? If not, try to reverse its legs in the playdough.

Circuit D – Get Creative

Try to sep up your circuits with different shapes and configurations of both playdoughs.
Change the LED with other electrical component you have.

What’s going on here?

How an electrical circuit works?

Electricity is the flow of electrons in a loop made of conductive materials, materials that allow that flow. In order for a circuit to work we need a power source (the batteries in our case). In an electric circuit, the electrons always flow form the negative terminal of the power source to the positive terminal, and from the positive terminal to the negative one when flowing inside the power source. Since we can’t see the electrons , in order to know the circuit works, we need an electrical component that will tell us electricity flows, like LED, buzzer, computer, washing machine and so many more!

How come the playdough can be conductive or insulating?

Look again at the ingredients list. See the differences? In the conductive dough we used salt and cream of tartar. In the insulating one we replaced the salt with sugar, the tap water with distilled water and didn’t add cream of tartar at all.
Why? Because the conductive properties of all these ingredients!
Table salt is a chemical that is made of ions, sodium ions and chloride ions. That means it contains electrical charges which allows the flow of electrons. Same goes with the cream of tartar. Cream of tartar is another type of salt, although it doesn’t contain sodium or chloride, but other kind of ions. Cream of tartar, by the way, is the magic ingredient that turns a regular dough into a playdough, and that’s the reason the insulating playdough is not as fun to play with.
In the insulating playdough, we exchanged the salt with sugar. Sugar, doesn’t contain ions, thus it doesn’t conduct electricity. Same with distilled water. Distilled water is water from which the salts were removed, and since it contains no salt, it doesn’t conduct electricity. Did you know, the very low levels of different salts in our tap water are what makes tap water tastier than the taste-less distilled water.

So now that we understand what’s going on in the playdough lets talk about the circuits we built:

Why doesn’t the LED always work?
LED stands for Light Emitting Diode. As opposed to a wire or incandescent light, a diode is en electrical component that conduct electricity only in one direction. Therefore, the direction of the LED in the circuit is crucial for lighting it.

Why the light went off when the 2 conductive balls were brought into contact?

Well, what we did here is called short circuit. It means we gave the electrons a shortcut, an easier way to go through the circuit. And since nature always prefers the easiest route, most of the electrons take that shortcut and the LED doesn’t get enough electrons or electricity to lit.

Keep on experimenting!

Move on to the more advanced playdough experiment “In Parallel or Series? Which Way to Go?

Share it with us!

Send us your circuits pictures and we’ll post them here!

Reference: http://courseweb.stthomas.edu/apthomas/SquishyCircuits/index.htm