第1个回答 2011-11-28
Electromagnetic induction and a moving microphone
in 1831, the physicist faraday discovered electromagnetic induction phenomenon ：Circuit of the body in a magnetic field cutting the line to any movement, the conductor can produce electric current, this phenomenon is called the electromagnetic of all phenomena is called "the current
Electromagnetic induction is an important discovery. for humanity's greatest contribution is made out of the generator, that large scale power become a reality.
Electronic generators are using electromagnetic induction , which might made people are aware of some physical knowledges.In fact, you may not know, we in the life of the receiver as the microphone shown in the picture(left), is based on this principle.
The receiver are many kinds of the different structures generally divided into a crystal move, type, the charcoal particles type, aluminum with and capacitance restaurants etc;In the use performance can be divided into the microphone, stereo, land-based and wireless the receiver in a body and received: in the direction and can be divided into the heart, before his heart and strong point, no direction. But no matter what kind of the receiver,they are based on the same principle, which is to transfer sound signals into electronic signals, but the transformation has different ways.
Most commonly used in our lives is still the microphone, its structure is shown in the right picture. It in a diaphragm paste with paint in the coil, also called the voice coil. there are diaphragms the installation of a circle and the permanent magnet in a coil of a permanent magnet on either side of the coil transforming out.
We already know, the body by the sound. we will work round to the spread of the waves. waves cause the air around to vibrate. Into the microphone to speak, when we speak of the waves will cause diaphragm oscillation. The vibration of diaphragm will have brought in a track on the back of a coil, and the coil vibrates.By cutting the line, the sense of the coil produces the sound current, and thus transform into electrical signals.
Our voice is constantly changing, and vibration to a coil of the current size and field is constantly changing, and it changes an amplitudeand a frequency is determined by the waves
Of course, the light of current does not cause the speaker of the vibrations when we use a loudspeaker the current enlargement, to speakers from the speakers gave the amplified sound.
In the eighth grade（people studying version: taught you how to study physics) have mentioned this problem: "When you speak or sing to the microphone, producing the sound of the diaphragm______, and diaphragm connected with the coil also ______, the coil in the field of the motion can create the sound changing with the change of voice ______, the enlargement of that restores voice."
The answer is: vibration, vibration, the current
Loudspeakers' working process is just and microphone completely on the contrary , it puts electronic signals also converse into voice signal, which uses the principle that conductors in a magnetic field will be forced. Students who are interested in this can look for some information, checking about the structure and working process of loudspeaker.
When we sing at karaoke and KTV，when we enjoy the performance of singers on the stage, when we are devoted in the speaking of hosts, please don't forget the silent tool holding in our hand－－microphone, without their existence, we can not enjoy what we own.
第2个回答 2011-11-28
The electromagnetic induction and the moving-coil microphone
In 1831, the British physicist Faraday invented the electromagnetic induction phenomenon: the closed circuit of portions of the conductor in a magnetic field for cutting magnetic induction line movement, conductor will produce current, this phenomenon is called the phenomenon of electromagnetic induction, the current is induced current.
Electromagnetic induction of this important invention, the greatest contribution is the result of produce generator, so that the human large-scale electricity becomes a reality.
The generator is the use of electromagnetic induction phenomenon made, it may have some knowledge of physics of the people know. In fact, you may not know, we live in a common transmitter ( microphone ) figure ( left ), most of them are based on this principle.
Microphone type are many, according to different structures, generally divided into moving coil type, crystal type, particle type, aluminum belt and capacitance type: according to the use of performance can be divided into a stereo microphone, wired microphone, wireless microphone, electret microphone: according to the receiving direction and can be divided into heart, super cardioid, strong point without direction, etc.. But no matter what form of the microphone, the principle is the same, the acoustic signal is converted into an electrical signal, using only a switching signal in different ways.
We live in the common microphone mostly moving-coil microphone, its structure as shown in the figure (right ): it in a diaphragm back paste a wire coil wound, also called voice coil. The diaphragm is arranged behind an annular permanent magnet, and the coil in the permanent magnet of a pole, the two ends of the coil with leads.
We already know, objects are represented by a vibrating sound. When we speak up around the propagation of acoustic waves, sound waves caused by the surrounding air vibration. To speak into the microphone, we speak of sound waves generated by the vibrating diaphragm diaphragm will, vibration to drive the sleeve in magnetic pole coil and coil before and after vibration, and vibration, do the cutting the magnetic induction lines motion, so is generated in the coil current, so the sound signal into electrical no..
Our voice is size changing, coil vibration generated when the induced current size and will continue to change, it changes the amplitude and frequency is determined by the acoustic wave.
Of course, the weak current is sufficient to cause the speaker the speaker vibration, then we use a loudspeaker ( commonly known as power amplifier ) to the current amplification, and then passed to the speaker, from the speaker sends the amplified sound.
In the eight grade ( person teaching edition ) work skills physics was mentioned in the question:" when you to speak into the microphone or singing, sound generated by the diaphragm _ _ _ _ _ _, diaphragm and coil connected with _ also _ _ _ _ _, a coil in a magnetic field of this movement, can produce with the sound changes in the _ _ _ _ _, magnified, reduced to sound through the speaker."
The answer is: vibration, vibration, current
The speaker and microphone just the opposite, the electrical signal is converted into a sound signal, used here is the electrical conductor in magnetic field can be affected by the force of this principle, interested students can look up information, have a look the speaker structure and working principle!
When we sing karaoke OK office, when we were in KTV rooms enjoy singing, when we revel in the stage singer's wonderful song, when we immerse in the host's witticism Lianzhu, please don't forget to take in hand the silently from the tool -- the microphone, not their existence, not their due diligence, how come we can have so good?