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Facilitator/Educator Guide: Squishy Circuits

This project offers a fun way to introduce your students to electrical circuits using materials they are already familiar with: Play-Doh® and modeling clay. You can combine these materials with a battery pack and tiny lights, called LEDs, to make a simple circuit, allowing you to "light up" an art project.

Activity's uses: Demonstration or small group exploration
Area(s) of science: Physical Science
Difficulty level:
Prep time: < 10 minutes
Activity time: 20-30 minutes
Key terms: Electricity, conductor, insulator, circuit, open circuit, closed circuit, short circuit
Downloads and Links: Facilitator / Educator Guide PDF.
Student Guide web page or PDF.

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Background Information

The following two videos will walk you through setting up and using Squishy Circuits as a classroom activity, and the circuit concepts you can use them to teach your students.


Video 1: Introduction and basics.
Video 1: Introduction and basics. https://www.youtube.com/watch?v=GBuWiFM2T_o


Video 2: Circuit terminology.
Video 2: Circuit terminology. https://www.youtube.com/watch?v=jbryDvZ7UuM

A circuit is a path through which electricity can flow. Circuits can be very simple, like the ones you will build in this project that just have a battery and a light; they can also be very complicated, like the ones inside a computer that contain thousands of parts. Circuits are made of conductors, or materials that allow electricity to flow easily. Most metals are good conductors, but as it turns out, Play-Doh is also a conductor! Materials that do not let electricity flow easily are called insulators. Most rubbers and plastics are insulators. Look around your classroom for wires like power cords and computer cables. They all have metal conductors on the inside, and are covered in plastic or rubber insulation, which prevent you from getting shocked.

In this project, your students will build a simple circuit with a battery, Play-Doh, and a tiny light called an LED (which stands for light-emitting diode—the type of tiny lights found in many electronic devices). In order for the LED to light up, there needs to be a complete path from the battery's positive (+) terminal, through the LED, and back to the battery's negative (-) terminal. This is called a closed circuit. If the path is broken somehow, then electricity cannot flow in a complete loop, and this is called an open circuit. Finally, electricity likes to take the "path of least resistance." If electricity can flow directly through Play-Doh instead of the LED, this creates a short circuit and the LED will not light up. Figure 1 shows all three types of circuits. You will walk your students through creating each type of circuit, and then let them build their own sculptures with a proper closed circuit.

Open, closed, and short squishy circuits
Figure 1. Open, closed, and short circuits. Notice how the LED only lights up with a closed circuit.

For Discussion

This activity can be used to introduce several basic concepts about electricity. For example:

  • Ask students which materials in your classroom they think are conductors, and which are insulators (for instance, paper clips are conductors, wooden pencils are insulators).
  • Ask students to name circuits that they see or use in everyday life (like lamps, appliances, and computers).
  • Ask students where electricity comes from to power their circuits (for instance, some circuits plug into wall outlets, some are battery powered).

Materials

Optional for preparing ahead:

  • To decrease project cost, you can follow a recipe to make homemade insulating and conductive dough using basic kitchen ingredients, instead of using store-bought Play-Doh and modeling clay. This requires a stove, basic kitchen utensils, and large resealable plastic bags in which to store the dough so it does not get moldy. If you do not have access to these items at school, you will need to prepare the dough at home the night before class. For directions on how to make your own dough, see Electric Play Dough Project 1: Make Your Play Dough Light Up, Buzz, & Move!.

Needed for each demo or small group at the time of the activity:

  • Squishy Circuits Kit (1), available from the Science Buddies Store.
    • The kit includes:
      • DC hobby motor
      • Piezoelectric buzzer
      • Mechanical buzzer
      • 4xAA battery holder (batteries not included)
      • Jumbo LEDs (25 total: 5 each in red, green, white, yellow, and blue)
      • Conductive play dough recipe
      • Insulating play dough recipe
    • For each group, you will need these parts from the kit:
      • 4xAA battery holder
      • LEDs (5, one of each color)
      • AA batteries (4)
      • Jars of Play-Doh (2) or lump of homemade conductive dough
      • Stick of modeling clay (1) or lump of homemade insulating dough
squishy circuit materials
Figure 2. The materials needed for each group.

What to Do

Prepare Ahead (< 10 minutes)

  1. Insert four AA batteries into each battery holder, as shown in Figure 3. Pay attention to the "+" marks on the batteries and make sure they line up with the corresponding "+" symbols inside the battery holder (just like putting batteries in a television remote control). Make sure the battery pack's power switch is in the "off" position.
4xAA battery holder
Figure 3. Insert the four AA batteries into the battery holder.
  1. Important Safety Note: During the project, it is important not to let any metal parts (the battery pack prongs or the leads of the LEDs) touch each other directly. Metal parts should always have a lump of Play-Doh in between them; otherwise, this can create a short circuit and cause the circuit parts to get very hot. Short circuits can also permanently burn out LEDs. Figure 4 shows some examples of short circuits. If you notice a student's Play-Doh turning black or bubbling, or they say their circuit feels hot, turn off the battery pack and correct any short circuits before proceeding.
short circuits to avoid
Figure 4. Avoid short circuits! Do not let the metal battery pack prongs touch each other, and do not let the LED leads touch the battery prongs directly.
  1. Place one Squishy Circuits kit, two jars of Play-Doh (or lump of homemade conductive dough), and one stick of modeling clay (or lump of homemade insulating dough) at each workstation.

Science Activity (20-30 minutes)

  1. Tell each group to take two lumps of Play-Doh and stick one metal prong from their battery pack into each lump, as shown in Figure 5.
squishy circuit play doh
Figure 5. Insert one metal prong into each lump of Play-Doh.
  1. Tell each group to look closely at an LED from their kit. The tiny metal legs that stick out of an LED are called leads (pronounced "leeds"). The LED has one longer lead and one shorter lead, as shown in Figure 6. Bend the leads apart slightly.
LED leads bent
Figure 6. The long and short leads of an LED can be bent apart slightly.
  1. Tell each group to insert the longer LED lead into the lump of Play-Doh connected to the red battery pack wire, as shown in Figure 7. Important: Do not let the LED lead touch the metal prong from the battery pack directly, as this will create a short circuit. There should be some Play-Doh in between.
LED long lead positive connection
Figure 7. Longer LED lead connected to Play-Doh lump that is connected to the red wire.
  1. Now, ask the students to turn their battery pack power switches to "on." What happens? Nothing! This is because they still have an open circuit. They need to close the loop in order for electricity to flow. Have them turn the battery packs back to "off."
  2. Now, tell the students to connect the shorter LED lead to the lump of Play-Doh connected to the black battery pack wire, as shown in Figure 8. Turn the battery pack back "on." What happens? The LED should light up, because you now have a closed circuit!
    1. Troubleshooting: Some students might have put their LEDs in backwards (gotten the long and short leads reversed). If an LED does not light up, have them try flipping it around.
    2. Also, make sure the Play-Doh is squeezed firmly around the battery pack prongs and LED leads. If these are loose and wobbly, it can cause the LED to flicker.
LED short lead negative connection
Figure 8. The LED should light up when you have a closed circuit.
  1. Now, tell students to leave the battery pack on, and push the two lumps of Play-Doh together, as shown in Figure 9. The LED should go out! This is because they have created a short circuit. The electricity takes the "path of least resistance" and flows directly through the Play-Doh instead of going through the LED.
squishy short circuit
Figure 9. The LED will go out when the students create a short circuit.
  1. Ask students how they think they can prevent a short circuit. Remind them that Play-Doh is a conductor, but modeling clay is an insulator. You can do this by adding a piece of modeling clay between the lumps of Play-Doh, as shown in Figure 10. Have your students try this, and the LED should light up again!
squishy circuit with modeling clay insulation
Figure 10. Modeling clay can be used to prevent short circuits since it is an insulator.
  1. What if you want to add more LEDs? You can have the students insert more LEDs right alongside their first LED, as shown in Figure 11. Remember that the long leads need to be inserted in the Play-Doh connected to the red wire, and the short leads should be inserted in the Play-Doh connected to the black wire.
squishy circuit with 3 LEDs in parallel
Figure 11. A circuit with three LEDs.
  1. Use the remaining time to let students experiment and build their own light-up sculptures. Animals with LED "eyes" are a popular project. Make sure they remember to use modeling clay to avoid short circuits.
  2. Optional: you can let the students experiment with the motors and buzzers that came with the kit.
    1. Important: the buzzers are loud. We do not recommend letting an entire class of students use the buzzers all at once.
    2. The buzzers and motors require much more electrical current than the LEDs. Therefore, they will only work with short, thick lumps of Play Doh. If you try to connect them to the battery pack using long, thin rolls of Play Doh, they will not work.
    3. The buzzers and motor each have one red and one black wire. For the buzzers, you need to match the wire colors to the battery pack (red to red and black to black). If you connect them backwards, they will not work. The motor can actually be connected in either direction. Reversing the wires just reverses the direction the motor will spin.
  3. Clean-up:
    1. Make sure all battery packs are turned off.
    2. Use a damp paper towel to wipe off the LED leads and the battery pack prongs, to clean off any excess Play-Doh or modeling clay.
    3. Use a dry paper towel to dry off the LED leads and battery pack prongs.
    4. Store Play-Doh, modeling clay, and any homemade dough in airtight containers. Homemade dough can be refrigerated to extend its lifetime, as it may become moldy after about a week at room temperature.

Expected Results

All students should be able to get at least one LED to light up. The most common cause of a circuit "not working" is that the student has the LED in backwards. The second most common cause is that the battery pack prongs are too loose, so make sure the Play-Doh is packed tightly around them. Also remember to avoid short circuits; do not let the metal parts (battery prongs or LED leads) touch each other directly.

For Further Exploration

This activity can be expanded to teach more circuit concepts; for example:

  • Use it to teach the difference between series and parallel circuits. Figure 12 shows a series circuit and Figure 13 shows a parallel circuit (what your students did in this project). Parallel circuits are better for connecting LEDs because if one LED goes out, the other ones stay lit. The LEDs also all stay about the same brightness. In a series circuit, each successive LED gets dimmer, and if one LED is removed, the other ones will go out.
squishy circuit in series
Figure 12. You can create a series circuit by connecting LEDs "in a line," using alternating lumps of Play-Doh and modeling clay. The LEDs rapidly get dimmer as you add more, so this is not a good way to connect LEDs.

squishy circuit in parallel
Figure 13. You can create a parallel circuit simply by adding more LEDs next to each other. Here the LEDs all have the same brightness.
  • Use the materials to teach about electrical resistance, or how much a material resists the flow of electricity. Even conductors have some resistance. What happens if you connect an LED using very long, thin rolls of Play-Doh instead of short, fat lumps? Ask your students to try this out on their own. As shown in Figure 14, the LED gets dimmer because the long, thin rolls have a higher resistance.
resistance of long strand of play doh makes LED dimmer
Figure 14. The LED gets dimmer when connected with long, thin rolls of Play-Doh. This difference in brightness between the LEDs may be easier to see in a darker room, so try turning off the lights or closing window blinds.
  • Have your students experiment with the other components in the kit, like the motor and buzzers. Can they make circuits with motion and noise instead of just light?

Credits

Ben Finio, PhD, Science Buddies
Squishy Circuits were originally developed by the Thomas Lab at the University of St. Thomas.

Play-Doh® is a registered trademark of Hasbro.

Sponsor

This project was sponsored by General Electric.