Conductor vs. insulator
Conductors and Insulators
- Grades 3-8
- 15 minute activity
- NGSS 5-PS1-3
Quick answer
A conductor is a material that lets electricity flow through it easily, like metal, salt water or salty play dough. An insulator is a material that blocks electricity, like rubber, plastic, wood or glass. Circuits need both: conductors carry electricity where it should go, and insulators keep it from going where it should not.
What is a conductor?
In a conductor, some electrons are loosely held and can move easily from atom to atom. When a battery gives them a push, they flow along, and that flow is electricity.
Good conductors include:
- Metals like copper, aluminum, steel, silver and gold. Copper is used inside most electrical wires.
- Salt water and other water with minerals dissolved in it.
- Salty play dough, which is why you can build circuits with it.
- Graphite, the "lead" in a pencil.
What is an insulator?
In an insulator, electrons are held tightly in place and cannot flow, so electricity is blocked. Common insulators include rubber, plastic, glass, dry wood, paper, air and dough made with sugar instead of salt.
Look at any power cord and you will see both at work. Inside is copper wire, a conductor that carries the electricity. Around it is a plastic or rubber coating, an insulator that keeps the electricity in the wire and away from your hands.
Conductor vs. insulator at a glance
Conductors
- Let electricity flow easily
- Electrons can move freely between atoms
- Examples: copper, aluminum, steel, salt water, salty dough
- Used for: wires, plugs and circuit paths
Insulators
- Block the flow of electricity
- Electrons are held tightly in place
- Examples: rubber, plastic, glass, wood, air, sugar dough
- Used for: wire coatings, handles and keeping circuits apart
Why does play dough conduct electricity?
Have you ever tasted play dough? It is salty. When salt dissolves in the water in the dough, it splits into tiny charged particles called ions. Those ions can move through the dough and carry electricity with them.
Insulating dough swaps the salt for sugar. Sugar dissolves too, but it does not split into ions, so the electricity has nothing to carry it. Make it with distilled water, because tap water has minerals that can let a little electricity through.
Want to make your own? Our free dough recipes show how to make both conductive and insulating dough at home.
Try it with dough
Make a conductor tester
Turn a dough circuit into a tester that tells you whether any object is a conductor or an insulator.
You need
- Battery holder with 4 AA batteries
- Conductive (salty) play dough
- 1 LED
- Objects to test: paper clip, coin, foil, plastic pen, rubber band, craft stick, paper, white insulating dough
Steps
- Make three pieces of conductive dough and line them up with a small gap between each piece.
- Push the red battery wire into the first piece and the black wire into the third piece.
- Put the LED across the first gap: long leg in the first piece, short leg in the middle piece.
- Switch the battery holder on. The LED stays dark, because the second gap breaks the loop.
- Press an object across the second gap so it touches both pieces of dough.
- If the LED lights, the object is a conductor. If it stays dark, it is an insulator. Write down your results.
What happens
Metal objects like paper clips, coins, keys and foil light the LED. Plastic, rubber, wood, paper, glass and white sugar dough keep it dark.
Not working?
Nothing lights up at all? Push the middle and last pieces of dough together for a second. The LED should light. If it does not, flip the LED around and check the batteries.
Key words
- Conductor
- A material that lets electricity flow through it easily.
- Insulator
- A material that blocks the flow of electricity.
- Electron
- A tiny particle with a negative charge. Moving electrons carry electricity in metals.
- Ion
- An atom or group of atoms with an electric charge. Ions carry electricity through salt water and salty dough.
- Resistance
- How much a material pushes back against electricity. Conductors have low resistance and insulators have very high resistance.
- Electric current
- The flow of electricity through a circuit.
For teachers
The conductor tester supports NGSS 5-PS1-3: make observations and measurements to identify materials based on their properties, including electrical conductivity. Have students predict whether each object will conduct, test it, record the result in a table and look for patterns (all the metals conduct). It also connects to 4-PS3-2.
Find free lesson plans on our education page.
Watch: conductors and insulators
Conductor and insulator questions
Is play dough a conductor or an insulator?
Regular play dough is a conductor, because it contains salt. Dissolved salt forms ions that carry electricity through the dough. Dough made with sugar instead of salt is an insulator.
Is water a conductor?
Pure water is a poor conductor. Tap water, salt water and the water in our bodies have minerals and salts dissolved in them, and those make water a good conductor. That is why water and electricity are a dangerous mix.
Is the human body a conductor?
Yes. Our bodies are mostly salty water, so electricity can flow through us. That is why wall outlets and power lines are so dangerous. A battery pack with four AA batteries is too weak for you to feel.
Is air a conductor or an insulator?
Air is an insulator. That is why a small gap between two pieces of dough is enough to stop the electricity. Only extremely high voltages, like lightning, can push electricity through air.
Is wood a conductor?
Dry wood is an insulator. Wet wood can conduct a little electricity, because of the water and minerals inside it.
What are some examples of conductors and insulators?
Conductors: copper, aluminum, steel, silver, gold, graphite, salt water and salty play dough. Insulators: rubber, plastic, glass, dry wood, paper, cloth, air and sugar dough.
Printable guide: Circuits Explained (PDF)
Next, try a project
Try the Conductor Project A free step-by-step project with printable instructions.