What will you get if you make speakers out of yogurt cups? Some practical application of electromagnetism.
What you will need:
- 2 round shaped magnets (½ to ¾ inch in diameter)
- 1 D-cell battery
- 1 yogurt cup (or any similar container like whip topping, butter, etc)
- 15 ft coil wire with 20-24 gauge (ideally the enamel-coated transformer coil wire)
- Sandpaper
- Electrical tape
- Radio with output of at least 20 watts and detachable speakers
What you need to do:
- Create an electromagnet by winding 6 to 15 feet of wire around the D-cell battery. Make sure to leave 2 inches of the wire hanging on each end.
- Once the wire is wound, carefully remove it so the coiled wire will retain its shape. Tape the coil to keep it from unraveling.
- Remove 1 inch of the enamel insulation by rubbing the ends of the wire with sandpaper.
- Hold each end of the wire on each end of the battery to create a series circuit.
- Take a magnet and move the coil near it. Observe the motion of the coil. If the coil is connected to the battery differently (try switching the wires connected to the ends of the battery), it will react differently to the magnet. This is because the poles of the electromagnet are reversed.
- Get the plastic container and attach the coil and the magnet to the bottom of the cup. You can put the magnet inside the bottom of cup while the coil on the outside of the bottom of the cup. The coil and the magnet should be next to each other. The ends of the coil should be free. Use tape or glue to make the attachment permanent.
- Connect the ends of the coiled wire to the speaker output of the radio. At the back of the radio, there are usually holes where you insert plugs. This is where you can insert the end of the coiled wire from the yogurt cup. One wire should be connected into the hole that will activate the left speaker and the other into the hole that will activate the right speaker.
- Turn on the radio. Adjust the volume to control the current that flows through the wire coil. This will increase or decrease the electromagnetic force. When the current coming from the radio is fast, the generated electromagnetic force will cause the yogurt cup to vibrate. This vibration can be heard.
What did we learn:
- There are four different energy forms used here: heat, electrical, magnetic and mechanical.
- The project used a circuit in series because there is only one path.
- Both a conductor and insulator is used – the wire is the conductor and the enamel cover is the insulator.
- The strength of the speaker and the electromagnet can increase by wrapping more coils.
- When the volume is high, the electricity flowing through it increases. When this happens, the resistance in the wire will cause the electrical energy to convert into heat energy. Turn down the volume to reduce the heat from the wire.
Read more posts about experiments with batteries.
