Speaker principle
Loudspeakers use electromagnets to convert current into sound. It turned out that current and magnetic force are closely related. Try winding the copper wire on the iron plate, and then connect the small battery, you will find that the iron plate can suck up the 4D clip. When a current passes through the coil, a magnetic field is generated, and the direction of the magnetic field is determined by the right-hand rule.
The speaker uses an electromagnet and a permanent magnet at the same time. Assuming that the C tone is now played (frequency is 256Hz, that is, 256 vibrations per second), the phono will output 256Hz AC. In other words, the direction of the current within one second will be Change, 256 times. Each time the current changes direction, the direction of the magnetic field generated by the coil on the electromagnet changes accordingly.
