Who lets current through?

The idea

Materials through which electric current can flow easily are good conductors (conductors of electricity); materials through which current cannot pass are insulators (poor conductors of electricity).

Fill the gap

Put a lamp, a cell and a gap in a circuit. Fill the gap with different things. The lamp glows for some materials only.

Which kind of thing do you think lets the current through?

• Metal things, like a nail
• Plastic and rubber things
• Anything works the same

The gap test

Put each thing in the gap. First guess, then see what the lamp does.

Conductor or insulator

Materials through which electric current can flow easily are good conductors (conductors of electricity). Materials through which current cannot pass are insulators (poor conductors of electricity).

Your table shows a pattern: the lamp glowed for the metal things and stayed dark for the plastic, rubber and ceramic things.

• If the lamp... | Current... | The material is a...
• glows | passes through it easily | conductor (good conductor)
• stays dark | cannot pass through it | insulator (poor conductor)

Notes

Conductors let current flow easily and make the lamp glow. Insulators stop the current and the lamp stays dark.

Check yourself

The lamp stays dark when a rubber eraser is put in the gap. The rubber eraser is a...

Which of these is a good conductor of electricity?

A material that lets current flow easily is called a...

Our body is a conductor of electricity. What is the safe rule?

• conductor. A conductor would let the lamp glow.
• insulator — correct. Yes! Current cannot pass through it.
• cell. A cell is a source of energy, not a material in the gap.
• A plastic ruler. Plastic is an insulator.
• An iron nail — correct. Yes! Metals let current pass easily.
• A ceramic cup. Ceramic is an insulator.
• good conductor — correct. Yes! Also called a conductor of electricity.
• insulator. An insulator stops the current.
• filament. A filament is the thin wire inside a lamp.
• Touch switches with wet hands, to be quick. Never touch switches or plugs with wet hands. Current through the body can cause severe injury or death.
• Never touch switches or plugs with wet hands — correct. Yes! Our body conducts, so we keep our hands dry.
• Mend a plug with damaged insulation yourself. Never handle equipment with damaged insulation or broken plugs.