Light Sensitive Plane
Make a glowing paper airplane when it's bright outside!
Electricity is dangerous! Read this caution.
Materials: One airplane template, transparent tape, copper tape or aluminum foil, one LED, one photo resistor (also called a photo-conductive cell), one paperclip, and one 3V watch battery.
Fold Your Plane! Directions can be found on this page.
Note: Complete the Glowing Paper Airplane activity before attempting this project.
Add the three copper tape "wires" being careful to not rip or crinkle the tape.
Secure the photo resistor to the plane with transparent tape by placing one lead on each side of the copper wire gap. The photo resistor should extend above the wing fold (as shown).
Caution: As you secure the lead near the battery, make sure your transparent tape doesn't cover the wire to the battery.
Secure the LED to the the copper tape wires using transparent tape.
Secure the battery with a paperclip and enjoy!
The LED will likely light when you add the battery. Put your finger over the photo resistor and the LED will dim. If you enter a dark room or closet, the light may go out entirely.
Click to Read What's Happening
Remember that a complete circuit sends electricity from the power source (the battery) through the wires and components and back to the power source again. Some materials allow electricity to pass through them easily. These materials are known as conductors and include metals like gold, aluminum, copper, and iron. Other materials do not allow electricity to pass through easily. These are known as insulators and include materials like glass, rubber, paper, air, and plastic.
Some materials don't completely block electricity but resist it. Manufacturers can use these materials to make components that reduce the flow of electricity in a circuit. These components are known as resistors. Generally, resistors are static. They provide the same amount of resistance on a circuit all of the time. However, the photo resistor is a special type of resistor. The resistance it places on a circuit varies (or changes) based on how much light is in the surrounding environment. When a lot of light is present, resistance is small (allowing electricity to flow) so the LED lights up. When the surrounding light is limited, resistance increases so the LED gets dimmer or turns off entirely.
For more information on resistors, see this tutorial.
For more information about how resistance impacts electric voltage and current, see this tutorial.