6 Electromagnetic induction experiment
According to Fleming's law, when an electric current is passed through a magnetic field, a force works and vice versa. Opposition is also true for children. It is a unit that can convey the essence of science. The motor experiment page has the same principle, so please take a look.
Experiment 1: Paper cup speaker
Materials: Paper cups, cup noodle containers, PET bottles, and other items that are likely to be the main body of the speaker, enamel wire, etc. Ferrite magnet, enamel wire, motor
As shown in the figure above, attach a ferrite magnet and a coil of about 10 turns to a container such as a paper cup. After that, just connect it to the sound source and it will be fine? It will be a speaker. When the sound is quiet, increase the number of coil turns a little. Try to make the distance to the magnet as small as possible. If that doesn't work, an amplifier is introduced as usual.
In addition to paper cups, cup noodle containers are also recommended.
The reason why it makes a sound comes from Fleming's left-hand rule. When an electric current is passed through a magnetic field, the electric current receives a force. The audio signal from the sound source is flowing through the coil with an electric current. If there is a magnet there, the coil will be subject to force. It vibrates by this force. A sound is generated when the paper cup vibrates.
Experiment 2: Bone conduction speaker
you need : Motor, disposable chopsticks
The motor is made up of coils and magnets. Therefore, the motor also becomes a speaker. Of course, it sounds small when you put it on your ear, but you can make a hole in disposable chopsticks, insert it into the motor, and hold it in your mouth. Sound is transmitted through the skull . It is called bone conduction.
There is a crystal earphone. It is highly sensitive because it transmits sound by a piezoelectric element. This earphone is used for germanium radio and so on. If you connect these two as shown in the picture, you can have a conversation like an intercom.
Experiment 3: Easy linear motor car?
A linear motor car that uses the force applied to the flowing current according to Fleming's left-hand rule? To make.
you need : Aluminum pipe 2, ferrite magnet 10, construction paper, 3V power supply,
Prepare the ingredients. Place 10 ferrite magnets side by side on the construction paper and attach them. At this time, place it so that the same magnetic pole faces upward. Attach two aluminum pipes to the construction paper. Place it on the magnet and fix it.
Connect to a 3V power supply and place the aluminum pipe so that it drops from above. It moves to the left or right. The surface of aluminum is always aluminum oxide. This substance does not conduct electricity, so break it with a shock dropped from above to conduct electricity.
Experiment 4: Let's make "picopico" light
you need : film case, piezo element, LED, marbles, double-sided tape, awl
Attach double-sided tape to the piezoelectric element. Make a hole in the bottom of the film case and pull the cord out. Connect the cord to the LED. The longer leg is the plus, so connect it to the red cord. If you put a marble inside and shake it, the LED will light up every time the marble hits the piezoelectric element.
Experiment 5: Let's make a one-string electric guitar Let's make
you need : bolts, enamel wires, neodymium magnets, single-string guitars
Wrap the enamel wire around the bolt about 200 times. Attach a neodymium magnet to the bolt. Fix it under a one-string guitar (strings are iron) and connect it to the speaker through an amplifier. It doesn't make a lot of sound, so I'll make it a little better.
As usual, apply double-sided tape to the piezoelectric element. Stick it inside a stringed instrument toy. Connect to a seeker with an amplifier and play. There is speaker compatibility (impedance matching). Daiso's 300 yen speaker (upper right in the photo) is very compatible.
Experiment 6: Well, non-destructive inspection was this experiment! ??
you need : bolts, enamel wires, neodymium magnets, single-string guitars
If you drop a neodymium magnet inside a metal pipe that does not have a magnet instead of a plastic pipe, it will fall slowly. This is a very famous experiment. As shown in the photo in the middle, if the metal plate disappears in the middle, it will fall off quickly. This is because when the magnetic flux in the metal changes, an eddy current flows to compensate for the change. In the upper right figure, the red magnetic flux decreases as the north pole moves downward. An eddy current flows to make up for it so that a green magnetic flux is created. Then, the upper part of the metal plate will have an S pole on the surface . Inquire with N and S and fall slowly. By measuring this eddy current, the state of the metal inside the object can be inferred. It is one of the non-destructive inspections.