Warning! This should be a supervised activity. Take all safety precautions, including safety glasses. Use a low voltage power source. Start out by explaining the concept of an electrical circuit. This way, when building their own, they can trouble-shoot it as they understand the concepts behind what they're trying to build.
Here's how we did it.
You'll need the following items to make this circuit.
1. Cardboard rectangle, about 4" by 6"
2. 1 AA battery holder - 99 cents from Radio Shack (strip about 1/2" of wire ends, if needed)
3. 1 AA battery
4. 1 1.5V lamp - $1.49 at Radio Shack (strip about 1/2" of wire ends, if needed)
5. 2 brass fasteners
6. 1 paper clip
7. something to poke small holes in your cardboard - we used small screw drivers.
8. scotch tape
1. Lay the paper clip onto the cardboard about one inch from one of the narrow ends. With a pencil, mark the areas inside the paper clip curves. This is where you'll need to poke small holes for your brass fasteners to go through.
2. Poke holes where you've made the marks. We used small screw drivers. Place your small piece of cardboard on top of a scrap piece and push through at your marked locations. These holes should be just large enough to push the fastener through.
3. Place the battery and battery holder at the other short end of the cardboard, on the side we'll call the "front" or "top" of your circuit. We used scotch tape to hold it in place.
4. Make two holes near each battery holder end using the same method as above. The wire from each end of the battery holder should go through the hole onto the back of the cardboard.
5. Using the wire lengths on the lamp, determine a position for the lamp that's not too far away from both one of the battery holder wires and one of the holes made using the paper clip. Mark this position and make a hole in the cardboard for the lamp. Make sure it's not too big so the lamp will not pull through the cardboard.
6. Place one of the fasteners mostly through one of the holes you made using the paper clip. Holding the wire near the card, wrap the closest bare wire end from the battery holder around the base of the fastener. Open the fastener ends and spread tight to the card to maintain a good connection with the wire.
7. Place the lamp wires through the hole for the lamp. Use tape to hold the wires in place on the back of the cardboard. Take one of the lamp wires and twist it tightly together with one of the wires from the battery holder.
8. Holding the paper clip in place, with one of it's round ends over the holes made using the paper clip as a guide, place one of the fasteners through the paper clip and the hole. On the back side of the card, wrap the other lamp wire around the fastener as close to the cardboard as possible. Spread the fastener "wings" so that it keeps a tight connection to the lamp wire.
9. Put one fastener through one of the holes. Open the ends of the fastener on the other side so that they do not touch the other fastener ends. This would short your circuit!
10. With all the parts in place, your paper clip becomes your "switch" to turn your lamp off and on. Rotate the paper clip to touch the second brass fastener, and your circuit is "closed" and your lamp should light! Rotate the paper clip so it's not touching the other brass fastener and the circuit is open -- there will be no light.
11. When all done and you're sure it's working, secure wires and the fasteners to the cardboard with tape on the "bottom" or "back" side.
Troubleshooting: If it's not operating properly, check all your connections. Make sure you make a complete "circle" to complete the circuit. Then, consider the following variations!
What would happen if you used either larger or more batteries?
What would happen if you added another lamp in parallel? In series? Used another type of lamp? How would that affect the design?
Be safe and have fun!