Electricity seems like pretty magical stuff — subatomic force particles found in practically everything. The scientific term for these particles is “electrons,” and for the most part, the technology behind controlling them is very basic. “How basic?” you might ask. So basic that you can show your child how it all works from inside your home. With our Back-to-School Beginner Science Experiments about Electricity series, you and your kids will utilize similar materials and techniques used by Edison, Tesla, and other pioneers of electric energy when they began their experiments over a century ago.
The entire series has been leading up to this moment: you and your family can now build your own working radio from the privacy of your home kitchen. This experiment is a bit more involved than the last three, but if you successfully completed those, you should be ready for this one.
As before, let’s discuss the fundamentals:
While most of the materials you need are probably already in your home, you will need a few important things from a home improvement or hardware store.
- A Pair of Alligator Test Leads.These are wires with little clips at the ends that let you connect circuits.
- Enameled Copper Wire.This wire is used for making coils and has a thin coating of insulation.
While you won’t be needing to solder any connections in these circuits, you will need to double check that your connections are conducting electricity through them.
PLEASE NOTE: None of these circuits or their components are designed to be plugged into household wall sockets or use household current. They are too weak for that level of power and connecting them to household current is extremely dangerous.
Let’s start building that radio!
Building a basic radio isn’t hard. All you need is a coil, a point contact diode, an antenna, and a way to listen to it. That’s right — no battery needed. Also known as the “Foxhole radio,” you can make all this stuff in your kitchen!
Here’s How It Works
- You’ll need a short pine board for a base (though a thick piece of cardboard will do in a pinch).
- Next, take your enameled copper wire and wind it (like the electromagnet coil from Part 3) around a toilet paper tube 120 turns.
- Keep the loops around the coil neat and close together.
- Leave about an inch of stripped wire hanging loose on both ends. The right side of the coil will attach to the detector. The left side will connect to ground. (More on ground later.)
NOTE: In this experiment, the metal tacks acts as junctions for your connections, so you want your stripped wires to be in contact with each other and the metal tack.
Next, you’ll make a diode. A diode is a semiconductor that only lets electricity flow in one direction. Technically, what you’re actually making is called a “point contact diode” — but it’s usually called a “Cat’s Whisker Detector.”
- You’ll need a razor scraper blade from a home improvement or hardware store.
- The blade needs to be lightly oxidized or “blued.” This is done by holding it with a pair of pliers over an open flame until the metal glows red-hot and takes on a bluish-sheen at one end. (Only parents should do this.)
- Let the blade cool. (Seriously – “bluing” a blade means the razor blade is REALLY hot, so BE CAREFUL!)
- Insert one of wires from the coil underneath the blade.
- Insert one end of a long piece of wire under the blade. This long wire connects to the antenna wire.
- Anchor the wires at this end of the blade in place with a metal tack.
Make the other half of the detector by carefully sticking a safety pin into the graphite of a little stub of a pencil. Attach one alligator clip lead to the safety pin head. (This will connect to your headphones.)
Important Note: You move the pencil tip on the razor blade to find radio stations.
The antenna is a long, insulated wire. It should be about 30 feet long — although shorter lengths (10 to 15 feet) may work in population-dense urban areas. Your radio receiver collects the power from signals coming from radio stations by using an antenna. That’s why this radio receiver doesn’t use batteries.
If you don’t have an ear piece, you can use a pair of old headphones.
- Cut off the jack and separate the two cables from each other.
- Strip the insulation off from only one of the cables.
- Inside, there will be a common wire (usually bare) and an insulated “hot” wire surround by the common wire.
- Strip a little insulation from the hot wire. Keep the hot and common wires separate.
- Attach the hot wire to the wire coming off the safety pin head on the detector.
- Attach the common wire to the ground wire coming off the coil (left-side, see below).
Ground is the other half of the circuit, and it is called “ground” because it connects (eventually) to the earth itself. Connect a longer wire to the one coming from the left side of the coil.
At the end of this wire, you’ll need to:
- Add a wire that connects to the common wire of your headphone.
- Add a wire that connects to your kitchen faucet. Make sure your faucet and the area around your faucet is dry. (Most plumbing systems are grounded to the house electrical system.)
Now, put on the headphones and carefully adjust the pencil tip’s position on the razor blade. After some trial and error, you should be able to find a radio station – it’s not easy, and it does take patience. You might need to experiment finding the right place to put up your antenna. You might also find you get the best reception at night.
You can also add a tuning arm to pick up more radio bands and stations.
- You need is a thick, rigid piece of wire such as 9 to 12 inches of bare household grounding wire or even a piece of a wire clothes hanger sanded clean.
- Use sand paper to scuff a little of the lacquer insulation from the coil.
- Shape this tuning wire so it leans against the coil.
- Connect the ground wire to the end and secure both the wire and arm in place with a metal tack.
- Be sure that the tuning wire can swivel freely while maintaining contact with the coil and the long wire.
- Note: you may get better tuning results by detaching the wire from the left side of the coil and use only the ground wire and tuning arm.
We hope you enjoy your radio – and the sense of accomplishment that comes from building it yourself with your kid!
By the Way…
If you’ve had fun with these experiments, there are hundreds more you and your child can do together to learn even more about electricity. Two classic books that go into better detail about how electricity works are:
- Getting Started in Electronics by Forest M. Mims III
- 100 Amazing Make-It-Yourself Science Fair Projects by Glen Vecchione.
Do you have any beginner science experiments you’d like to share with our readers? Tell us about them in the comments!