Squishy schematics
Circuit Symbols and Schematics
- Grades 3-8
- 20 minute activity
- NGSS 3-5-ETS1
Quick answer
A schematic is a simple drawing of a circuit that uses symbols instead of pictures. Each part, like a battery, an LED or a switch, has its own symbol, and lines show how the parts connect. Engineers use schematics to plan, share and fix circuits, and you can draw one for any dough circuit you build.
Why draw a schematic?
A picture of a dough circuit shows colors and shapes. A schematic shows only what matters to the electricity: which parts there are and how they connect. That makes schematics quick to draw and easy for anyone to read, in any language.
- Plan a circuit before you build it.
- Share a circuit so someone else can build the same one.
- Fix a circuit by checking the build against the drawing.
From dough to schematic
Here is the simplest dough circuit and its schematic side by side. The shape of the dough does not matter in a schematic. A dough snake, a dough star and a wire are all drawn as straight lines, because they all do the same job: carry electricity from one part to the next.
To draw your own:
- Draw the battery symbol first, usually on the left side.
- Add a symbol for each part in the circuit.
- Draw straight lines to show each piece of dough or wire that connects two parts.
- Follow the path from the + side of the battery all the way around and back to the - side. If you can trace a complete loop through every part, your schematic is a circuit.
Reading the symbols
- Battery: long and short lines. The long line is the + side, where the red wire comes from.
- LED: a triangle pointing at a bar, with two little arrows for light. The triangle side is the long leg, and the triangle points the way the current flows.
- Switch: a line that lifts up like a gate. Drawn open, it means no current can flow.
- Motor: a circle with an M inside.
- Buzzer: a half circle on a line, with + marking the red wire side.
- Insulating dough is not drawn at all. In a schematic, a gap between lines already means no connection.
- Dots show junctions, the places where one path splits into two or more.
Try it with dough
Challenge: one switch, three LEDs
Build a circuit where one switch turns three LEDs on and off at the same time. Then draw its schematic.
You need
- Battery holder with 4 AA batteries
- Conductive (salty) play dough
- 3 LEDs
- 1 switch
- Paper and pencil
Steps
- Roll one small ball of dough and two long logs. Lay the logs side by side with a gap between them.
- Push the red battery wire into the small ball and the black battery wire into the bottom log.
- Push one switch wire into the small ball and the other switch wire into the top log. Now the switch is the only way across.
- Bridge the gap between the logs with three LEDs. Put each long leg in the top log.
- Flip the switch on and off. All three LEDs should turn on and off together.
- Draw the schematic: battery, switch, then three LEDs on their own branches between two lines.
What happens
The switch controls all three LEDs because every path to the LEDs goes through it. The LEDs are in parallel, so each one gets its own branch and they all stay bright. Learn more in Series and Parallel Circuits.
Not working?
One LED stays dark? Flip it around so the long leg is in the top log. All three dark? Make sure the small ball is not touching the top log, or the switch is being skipped.
More schematic challenges
- Light-up car: two LED headlights in parallel and a buzzer horn, all controlled by one switch. Draw it first, then build it.
- Swap and build: draw a schematic and trade with a partner. Can they build your circuit just from the drawing?
- Draw a project: pick a finished project, like the Rocket or the Stoplight, and draw its schematic.
- Find the mistake: draw a schematic with one error, like a backward LED or a missing line, and see if a classmate can spot it.
Key words
- Schematic
- A drawing of a circuit that uses symbols instead of pictures.
- Symbol
- A simple shape that stands for a part, like a battery or an LED.
- Junction
- A point where a path splits into two or more paths, shown with a dot.
- Branch
- One of the separate paths in a parallel circuit.
- Series
- Parts connected one after another on a single path.
- Parallel
- Parts connected on separate branches, each with its own path.
For teachers
This page follows Lesson 3 of our free NGSS curricula and educator guide, which includes worksheets for drawing squishy schematics. It supports NGSS 3-5-ETS1: define a problem, generate and compare solutions, and plan and carry out fair tests.
Have students sketch a schematic before they build, then compare the build to the drawing to troubleshoot. The challenge circuit is a good assessment: students who can explain why one switch controls all three LEDs understand both series and parallel paths. Find more lessons on our education page.
Schematic questions
What is a circuit schematic?
A schematic is a diagram that shows the parts of a circuit as symbols and the connections between them as lines. It shows how the circuit works, not what it looks like.
What is the symbol for a battery?
A battery is drawn as a pair of parallel lines, one long and one short. The long line is the positive (+) side. Several pairs together show several cells, like the 4 AA batteries in a battery holder.
What does the LED symbol look like?
A triangle pointing at a short bar, with two small arrows pointing away to show light. The flat side of the triangle is the long, positive leg. The triangle points in the direction the current flows.
Why do schematics use straight lines?
The exact path of a wire or a piece of dough does not change how the circuit works. Straight lines and right angles keep the drawing neat and easy to follow.
What does a dot mean in a circuit diagram?
A dot shows a junction, where wires are connected and the path splits. When two lines cross without a dot, they are usually not connected.
How do you draw a schematic of a play dough circuit?
Draw the battery symbol, add a symbol for each part (LED, buzzer, motor or switch) and connect them with straight lines wherever dough or wire joins them. Leave out insulating dough, since a gap between lines already means no connection.
Free NGSS educator guide (PDF). Lesson 3 covers schematics
Next, try a project
Build the Rocket Project LEDs, a buzzer and a switch in one build. Try drawing its schematic.