Safety NoteNeodymium magnets are very strong. Adult supervision is recommended when using the magnets. They can be difficult to pull apart, and pinch your fingers when they snap together. You should keep them away from small children or pets who might swallow them. You should keep them a safe distance (at least a foot away) from electronic devices.
- Optional: Use markers to decorate your plate, cup, or bowl. These directions will show a paper plate, but remember that you can also use a cup or a bowl.
- Wrap the magnet wire around your stack of magnets about 50 times to make a coil. Be sure to leave a “tail” of at least 15 centimeters of wire on both ends of the coil.
- Slide the coil of wire off the magnets, using your fingers to pinch it together so it does not unravel.
- Use a piece of clear tape to tape the coil down as flat as you can onto the bottom of a plate, bowl, or cup. Make sure the coil maintains a roughly circular shape and does not unravel. The back of the plate in this image has been colored with a marker, so it is easier to see the tape.
- Use a small piece of sandpaper to strip the insulation off the two ends of the wire (the “tails” of the coil). See the Science Buddies Wire Stripping Tutorial for detailed instructions, including a video. Make sure you do a good job stripping off the insulation, or your speaker will not work.
- Your 3.5 millimeter (mm) audio cable has two ends. One end has a regular “headphone plug” that will plug into the headphone jack on a computer, smartphone, tablet, or mp3 player. The other end has three wires—a red one, a white one, and a bare copper one. The red and white ones are the left and right audio signals (it is a “stereo” cable, meaning it has two separate audio channels for left and right speakers—but in this project you will only build one speaker), and the bare copper one is electrical “ground,” which is necessary to have a complete circuit for each audio channel (a complete circuit requires a closed path for electricity to flow “out and back,” which requires two wires, not just one).
- Plug the 3.5 mm plug into the headphone jack of your audio device, just like you would with a regular speaker or headphones.
- Connect the black alligator clip to the bare copper wire on the other end of the audio cable (the wire that does not have any colored insulation at all).
- Connect the red alligator clip to the exposed metal part of the red wire on the other end of the audio cable. Make sure you clip on to the exposed metal part, and not the red insulation. Leave the white wire unconnected.
- Connect the other ends of the alligator clips to the ends of the wire coil from your speaker. Remember that you should have stripped the insulation off these ends in step 5.
- Your paper speaker setup should now look like this.
- Play a song on your audio device.
- Use one hand to hold the paper plate up to your ear, with the coil of wire facing away from you. Use your other hand to hold the magnets just behind the speaker, right next to the coil of wire. Since you cannot see exactly where the coil of wire is, use your fingertips to feel for it, or have a volunteer help you line up the magnets. You should hear (faint) music!
- You can also stand the magnets up on a table, hold the edge of the paper plate with your hand, and hold the coil of wire just above the magnets. Put your ear close to the plate to hear the sound. Congratulations! You just built your own paper speaker.
- If you cannot hear any music, check the following:
- Make sure you are holding the magnets up against the coil axially (in other words, the cylindrical shape of the magnets should be lined up with the cylindrical shape of the coil, do not turn the magnets sideways). This ensures that the “push” from the magnets lines up with the “push” from the coil (see the Digging Deeper section to learn more about how this works).
- Make sure you sanded all the insulation off the ends of the magnet wire. Wire that has had its insulation removed should appear shiner and more “golden” colored, as opposed to the darker reddish color of the insulation. This is necessary so electricity can flow from the wire to the alligator clips. If you do not remove the insulation, the flow of electricity is blocked.
- Make sure the red and black alligator clips do not bump into each other. This will create a short circuit and prevent your speaker from working.
When you plugged your paper speaker into your audio device and played a song, you should have been able to hear very faint sound coming from the speaker. This happens because your audio device sends electrical signals to the coil of wire, which turns it into a temporary magnet. This temporary magnet pushes on the permanent neodymium magnets, causing the paper plate to vibrate. This vibration generates sound waves in the air that are picked up by your ear. The sound is very quiet because your speaker does not have an amplifier, which provides additional power to make the sound louder. Think about the difference between regular headphones and computer speakers that have their own power cord that plugs into a wall outlet. The headphones are relatively quiet, and you have to put them in your ears to hear them well. The computer speakers can be much louder because they get more power from the wall outlet, which creates bigger vibrations and makes louder sound. The paper speaker you made in this project is like the headphones—you have to hold your ear right next to it to hear the sound.