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A child tests objects on a small circuit with a battery, a bulb and two wires touching a coin, a rubber eraser and a pencil.

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Electricity: Conductors and Insulators

Test materials in a circuit.

Lesson 20 of 40

Try this first

Before we start

Today’s story

Electricity: Conductors and Insulators

Cruz looks at a power cord. The plug has two metal prongs. The cord has a rubber coat. The metal ends are bare. The middle is covered. He wonders why.

Electricity can move through some materials. These are conductors. Metals like copper, iron and aluminum are good conductors. Other materials block electricity. These are insulators. Rubber, plastic, wood and glass are insulators.

A cord uses both. Metal carries the electricity. Rubber keeps it from going where it should not. We can test any material with a simple circuit. Here are the steps.

See it

Five steps. Every time.

    Hands on

    Conductor Tester

    30 minutes · Do this with a grown-up nearby

    You need

    • One D battery
    • One flashlight bulb in a holder
    • Three pieces of insulated wire with bare ends
    • Tape
    • A paper clip, coin, eraser, wooden pencil, plastic spoon, aluminum foil, rubber band
    • Notebook

    Do this

    1. Connect one wire from the battery to the bulb holder.
    2. Connect the second wire from the holder to your test object.
    3. Connect the third wire from the object to the battery.
    4. Check that the bulb lights when you touch the two wires together.
    5. Place each material in the gap.
    6. Write bulb on or off.
    7. Sort into conductors and insulators.
    Write or draw: A table with Object, Predicted conductor yes or no, Bulb on or off, and Sorted as.

    Watch for: Notice that the pencil lead may work while the wood does not. Notice which materials surprise you.

    Safety: Use only a flashlight battery and never plug anything into a wall outlet.

    Same every time

    Three rules

    Rule 1Metals conduct.

    Most nonmetals insulate.

    Rule 2Test with a battery, never a wall outlet.

    Outlets are dangerous.

    Rule 3Record every result.

    Even surprises.

    Grandpa Fenn’s notebook

    Say it like a scientist

    conductor
    A material that lets electricity pass through.
    insulator
    A material that stops electricity.
    circuit
    A path electricity can follow.
    battery
    A source of electrical energy.

    Poppy’s quiz

    Six questions

    Tap an answer. Green means right. You will see why.

    Talk about it

    Say it out loud

    • How do you know a material is a conductor?
    • What is covered with plastic or rubber in your house to keep you safe from electricity?
    Did you know

    Pure water barely conducts. The minerals dissolved in tap water help it conduct, which is why water and electricity are dangerous together.

    Someone who does this

    An electrician chooses the right wire and covering for every job.

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