Conductors are substances that allow electricity to flow through easily.
Insulators are substances that don't allow electricity to flow through them.
Students built a conductivity tester out of an open circuit, bulb and two batteries. They replaced the opening with the object to be tested. If the object conducts electricity, the bulb lights up. If the object is an insulator, the bulb does not.
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| The metal spoon is a conductor and lights the bulb. |
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| The comb is an insulator and doesn't light the bulb. |
We also learned about switches using air as an insulator to prevent electricity from flowing. When the switch is open, electricity can't pass through the air, so the light turns off.
We found that shiny, metallic looking items often conducted electricity (like pyrite, metallic stickers, paper clips, and pennies.) Items made out of rubber, wood, plastic, cloth or painted were insulators (water bottle lid, plastic spoon, popsicle stick.)
We are actually conductors too (this is why we can get electrocuted!) We used a conductivity tester (with low voltage- of course) and made a circuit with our finger tips with the whole class as conductors.
Some objects allow electricity to flow through, but resist the flow. These are called resistors. Think of trying to swim quickly through a thick ketchup (you are the electrons, and the resistor is the ketchup.)
This causes friction which creates heat (try rubbing your hands together quickly to and see how hot they get or just remember the rug burn you got playing crab soccer.) If enough heat is created, it produces light. Old light bulbs work this way. They use a filament that resists the flow of electricity (that is why they get so hot!) We made our own light bulb today out of nichrom wire (a nice resistor.)
You can also find resistors in heaters, electric ovens, and toasters (spotted by finding glowing red coils.)
Try this virtual circuit tester from the BBC.
virtual circuit tester
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