synonymElectricity and magnetism(The mechanical transformation form of material energy in nature) generally refers to electromagnetism (physical terms)
Electromagnetic, one of the physical concepts, is a general term for the electrical and magnetic properties of matter.aselectromagnetic induction、electromagnetic wavewait.Electromagnetic is a Danish scientistOsterFound.Electromagnetic phenomenon is caused by charge movementwave, forming a magnetic field, so all electromagnetic phenomena are inseparable from the electric field.Electromagnetism is a branch of physics that studies the interaction between electric field and magnetic field, its laws and applications.Maxwell's hypothesis about changing electric field to produce magnetic field establishedelectromagneticsThe whole theoretical system ofelectricianandelectronic technique, profoundly affecting people's understandingMaterial worldThe idea of.
Electromagnetic is the reaction of energy, which is a general term for the electrical and magnetic properties of materials, such aselectromagnetic induction、electromagnetic wave, electromagnetic field, etc.All electromagnetic phenomena are inseparableelectric field；The magnetic field is generated by the moving charge (electricity).
Moving charges can cause fluctuations.The fluctuation mechanism is that when the moving charge e moves, it must be hindered by its neighbor e, which is shown by the moving charge driving its neighbor 1 to move upward, that is, the neighbor follows the moving chargeeMoving upward together;When adjacent 1 moves upward, it must be hindered by its own adjacent 1. It is shown that adjacent 1 drives its own adjacent upward movement, that is, adjacent 2 moves upward together with adjacent 1.In this way, it spreads forward and forms fluctuations.obviously,vacuumThe propagation speed of this wave islight speed。
Electromagnetic quality
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Electronic mass originated fromelectromagnetic fieldPart of.Its value can be changed fromUniform motionThe electromagnetic field momentum or basis of the electron,Mass energy relationFrom still electronicelectrostatic fieldEnergy estimates.stayElectronic theoryAt the beginning of the development ofElectromagnetic qualityEqual to the mass determined in the experiment.From this, we can calculate its radius, which is called the classical radius of the electron.
When an object has an electric field or a magnetic field, the object is electrically or magnetically shielded and weighed with a balance. For all devices (including the shield), the measured data is different from that without an electric field or magnetic field.
balanceThe data obtained by weighing is the mass. Due to the shielding of the object, the weighing process does not interfere with the balance.The weighing result data is valid.Therefore, for the same object, in addition to conventional mass, there is also electromagnetic mass.
Experimental methods
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Take linear current as an example, the fluctuation caused by the moving chargeNIn linear currentIOn the right side ofNSimplify to a ring currentabcdAlthough the pointa、b、c、dAre in linear currentIWithin the fluctuation range of, but pointsa、b、c、dThe energy of adjacent motion is unequal.obviously,Ea＞Ec，Eb=Ed。In this way, the linear currentIThe fluctuation of the small magnetic needleNRing current ofabcdThere is a clockwisemoment。This torque acts on the electron rotating around the core, making itClockwise rotationIts macro performance is small magnetic needleNThe north pole of the paper is vertical outward.
However, the fluctuation caused by current can have a small impactmagnetic needleDeflection of, indicating that the wave hasObjective reality；When two fluctuations with objective reality meet, they will definitely affect each other.
Linear currentI2 In linear currentI1,I1、I2 In the same direction and in the same plane, linear currentI1、I2 Divide the space intoA、B、CThree areas.Analyze linear currentI1. Adjacent motion formed during wave motion, known regionAThe energy of inner adjacent motion is greater than that of the regionCThe energy of inner adjacent motion.When linear currentI2. During wave propagationAThe resistance in the area is less than that in the areaCResistance within.Such currentI2 Fluctuating in the regionAPropagation speed invAWill be greater than in the areaCPropagation speed ofvC, i.evA＞vC。According to“Principle of invariance of light speed”This is unstable.So linear currentI2 Near linear currentI1 to makevA=vC=c, showing that the same direction linear current is attracted.
The movement of electric charges can produce waves.This fluctuation will not only affectSmall magnetic needleAnd the waves can also affect each other, thus successfully explainingElectromagnetic phenomenon。
It can be seen that starting from the moving charge and analyzing the fluctuation caused by the moving charge, we can get the so-called“magnetic field”；Analysis of the interaction between the two fluctuations can explain“Same direction linear current attraction”And other electromagnetic phenomena.
theoretical research
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Electromagnetism is a branch of physics that studies the interaction phenomena, laws and applications of electromagnetism and electromagnetism.
In the early days, because magnetic phenomena were once considered to be independent of electrical phenomena, and because of the development and application of magnetism itself, such as the development of modern magnetic materials and magnetic technology, the discovery and application of new magnetic effects and magnetic phenomena, the content of magnetism has been expanding, so in fact, magnetism has been studied as a parallel discipline to electricity.
Electromagnetism has developed from two independent sciences (electricity and magnetism) to a complete branch of physics, mainly based on two important experimental discoveries, namelyMagnetic effect of currentAnd changing magnetic field.
According to the viewpoint of modern physics, the phenomenon of magnetism is caused by moving charges, so it must contain the content of magnetism to varying degrees within the scope of electricity.Therefore, it is difficult to divide the contents of electromagnetism and electricity completely, and "electricity" is sometimes referred to as "electromagnetism".
maxwellElectromagnetic theoryThe significance of this theory lies not only in that it dominates all macro electromagnetic phenomena (including static electricity, stable magnetic field, electromagnetic induction, circuit, electromagnetic wave, etc.), but also in that it unifies optical phenomena within this theoretical framework and profoundly affects people's thinking of understanding the material world.
The discovery of electrons has made electromagnetism andatomAndMaterial structureThe theory of,Lorentz The theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron in the theory of electron.
Closely related to electromagnetism is classical electrodynamics, and there is no difference in principle between the two in content.Generally speaking, electromagnetism focuses on the experimental study of electromagnetic phenomena, and summarizes the basic laws of electromagnetism from a wide range of electromagnetic phenomenon studies;Classical electrodynamics focuses on theoryMaxwell's equationsandLorentz forceOn the basis of, we study the distribution of electromagnetic fields, the excitation, radiation and propagation of electromagnetic waves, as well as the interaction between charged particles and electromagnetic fields and other electromagnetic problems. In other words, the generalized electromagnetics includes classical electrodynamics.
Operation mode of electromagnetic energy
formula
In the stable state, the current waveform is as shown in Figure 1. At this time, the change of their magnetic flux increment △ Φ in the switch on ton time must be equal to the change in the flyback time.
Therefore, it can be seen from the above formula that if the working point with the same flux increment is established stably, the volt per second value of each turn of the primary winding of the transformer must be equal to the volt per second value of each turn of the secondary winding.
Figure 1 Current waveform under stable state
adoptControl switchThe conduction duty ratio of the tube is used to set the primarypeak current , however, inSwitch tubeWhen switching off, the output voltage and the number of secondary turns are constant, and the flyback working time must be self adjusted.
In the critical state, as shown in Is (2) in (a) of Figure 1, the flyback current just reaches zero before the next conduction time, and further increasing the duty cycle will causeconverterWhen the energy is transferred from complete to incomplete, the transfer function will become a two pole system with low output impedance. If moreelectric energyThe pulse width only needs to be slightly increased.In addition, in thetransfer functionThere is a "right half plane zero", which will lead to a 180 °phaseChange, which can also cause instability.
Storage and conversion of electromagnetic energy
As shown in Figure 2, when the switch tube V is turned on, it is the storage stage of electric energy. At this time, the transformer can be regarded as an inductance, as shown on the left side of (a) in Figure 2.
It can be seen from the left primary circuit in Figure 2 (a) and Figure 2 (b) that whenSwitch tubeWhen V is turned on, the current Ip of the primary winding increases linearly.magnetic coreInternalMagnetic inductionIncrease from Br to working peak Bm.
Figure 2 Buck BoostconverterAnd magnetization during energy storage and flyback
Figure 2
When the switch tube V is turned off, the primary current drops to zero.The rectifier diode D1 of the secondary is turned on and appearsinduced current。According to the principle of constant powerAmpere turnsIt is equal to the ampere turns of the primary winding.
During flyback, the flyback current gradually drops to zero, and the equivalent circuit is shown on the right side of (a) in Figure 2 and (c) in Figure 2.
For complete energy conversion, the flyback time is always less than the toff time.During the flyback time, the magnetic flux density of core b will drop from Bm to the residual magnetic flux density Bro, and the secondary current will decay at a certain rate, which is determined by the secondary voltage and secondary inductance. Therefore, U's is the voltage on the secondary winding, and Ls is the transformer inductance converted to the secondary.
Main impacts
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magnetic field
The magnetic field will cause serious harmful pathological changes and continuous changes of thinking in the human body.If human beings live in a strong magnetic field for a long timeEndocrine disorderDisorder, the brain will also produce abnormal continuous thinking, will induce some potential and special functional changes in the human body, will also induce cancer.But magnetic field and radiation are everywhere, so we don't need to worry too much in life.
(1) If you work in a strong magnetic field area, you should try to avoid contacting or staying away from the magnetic field source. The best way is to build a space building in a magnetic field free area that is resistant to magnetic field radiation interference.
(2) Those who often contact with strong magnetic field radiation sources should have regular physical examination and form a short-term cycle shift system.
(3) Do not abuse the magnetic therapy equipment, and follow the doctor's advice.
(4) Keep away from radio transmitting devices and areas with strong magnetic fields.
(5) Residential buildings should avoid the high-voltage transmission network, and the minimum spacing should be 300 meters away.
(6) The construction of strong electromagnetic wave transmitting sites should be far away from residential areas, and the spacing should not be less than 5000 meters.
radiation
Electromagnetic radiation, also known as electronic smoke, is caused byspaceThe electric energy and magnetic energy transferred together are composed, and the energy is generated by the charge movement;For exampleradio frequencyThe moving charge emitted by the antenna will generate electromagnetic energy.Electromagnetic "spectrum" includes various electromagnetic radiation, from extremely low frequency electromagnetic radiation to extremely high frequency electromagnetic radiation.There is alsoradio waves, microwave, infrared, visible and ultraviolet light, etc.The general definition of the radio frequency part of the electromagnetic spectrum refers to the frequency ranging from about 3 kHz to 300GihRadiation.
Electromagnetic beneficiation
1. Magnetic beneficiation with electromagnetic field
2. General term of magnetic ore dressing and electric ore dressing
Studies have shown that even under low intensity conditions, electromagnetic pulse stimulation can reduce abnormal neural connections in the brain and transfer them to the correct areas of the brain.The results of this study have been published in the Journal of Neuroscience.This finding is useful for the treatment of many patients with brain tissue abnormalitiesNervous system diseasesIt is of great significance, such as depression, epilepsy and tinnitus.[1]
Brain reorganization occurs in several different brain regions, covering almost the entire neural network.More importantly, this structural reorganization did not appear in the non abnormal brain regions of abnormal mice, which indicates that this therapy may only produce minimal side effects in the treatment of human beings.[1]
