Can you explain the formation and change of magnetic field with string theory?

The essence of the magnetic field is that it can convert magnetism into electricity, and at the same time, it can also convert electricity into magnetism.

I studied electrical engineering and automation, and I pondered for a long time about the electromagnetic theory before I could figure out the principles and build the electromagnetic theory into a framework. (The problems encountered are all ** thinking about the nature of magnetism), why can the energized wire deflect the nearby small magnetic needle, because the moving charge produces a magnetic field, and then briefly explain the Lorentz force, the moving charge will be subjected to a force in the magnetic field (left-handed rule), because the charge motion produces a magnetic field, and the interaction between the two magnetic fields is the Lorentz force, {The change of magnetic flux in the coil will produce an induced current (Lenz's law), and two parallel energized wires will attract or repel, To illustrate the first example, when a magnet is close to a coil, the free charge (sub) in the coil wire moves relative to the magnetic inductance line, which produces the Lorentz force, which causes the charge to move, that is, the charge in the coil moves to form an electric current, and the moving charge also produces a magnetic field, which is exactly the opposite direction of the applied magnetic field. The nature of the inductance is simply to say, after the coil is energized, assuming that the current is very slow, when it flows through each ring is analyzed separately, the magnetic field generated by the current (moving charge) in the previous coil acts on the next coil (before the current passes) will produce a reverse current to cancel, and the self-inductance phenomenon, that is, the voltage ahead current (there is an induced electromotive force but no current).

Here's the point: Why does a moving charge produce a magnetic field? Its essence is the electric field force, (which is the effect of relativity), and it is very cumbersome to use the relativistic effect to analyze, as shown in the following examples:

There is a section of energized wire (the positive and negative charges in the wire are the same density and are electrically neutral), and the current is generated by the directional movement of electrons, while the positive charge does not move. Suppose there is a positive charge next to the wire that is the same as the velocity (magnitude and direction) of the electrons in the wire, we are equivalent to the electrons and the positive charge outside the wire that do not move, and the positive charge in the wire moves in the opposite direction, according to the relativistic effect, the moving object will contract, that is, the positive charge in the wire will shrink due to contraction, so that the spacing becomes smaller and the density becomes larger, at this time, the wire is punctuality, and the Coulomb force (repulsion) generated by the positive charge outside the wire is what we think of as the Lorentz force. The essence of magnetism is another manifestation of the electric field force, and it can even be said that the magnetic field does not exist, but only refers to a physical model and notation for ease of use.

Magnets and other magnetic substances are the sum of the magnetic effects produced by the atoms that make up them, simply put, the magnetic field generated by the movement of electrons outside the nucleus (orbit around the nucleus, spin, etc.), and non-magnetic substances are not magnetic because the magnetic field generated by the movement of electrons outside the nucleus cancels each other out in different directions.

1. The probability of sinusoidal alternating current.

An electric current that does not change in magnitude or direction with time is called direct current.

The voltage that does not change with time, the magnitude and direction of the flow is called the DC voltage, and the electromotive force that does not change with the magnitude and direction of time is called the DC electromotive force. DC current, DC voltage, and DC electromotive force are collectively referred to as direct current.

The current that periodically changes in magnitude and direction with time is called alternating current, the voltage that periodically changes in magnitude and direction with time is called AC voltage purity, and the electromotive force that periodically changes in magnitude and direction with time is called alternating electromotive force. AC current, AC voltage, and AC electromotive force are collectively referred to as alternating current.

The current, voltage, and electromotive force that periodically change in magnitude and direction over time according to the sinusoidal law are called sinusoidal alternating currents, or alternated currents. Unless otherwise stated, the alternating current mentioned in the book refers to sinusoidal alternating current. The sinusoidal AC voltage waveform is shown in the figure.

Sinusoidal alternating current voltage waveform.

There are two kinds of alternating current: sinusoidal alternating current and non-sinusoidal alternating current according to the law of periodic change with time. The magnitude of the current, voltage, or electromotive force at a certain moment in time is called the instantaneous value, and if the horizontal axis is the time axis.

The curve obtained by using the magnitude of current, voltage, or electromotive force as the longitudinal axis and connecting the instantaneous values corresponding to each moment is called a waveform diagram or waveform curve, or waveform curve for short.

There are two types of common non-sinusoidal alternating currents: one is that the magnitude and direction change periodically, as shown in Figure (a) and (b); The other type of non-sinusoidal alternating current is called a pulse, as shown in figures (c) and (d).

Waveform diagram. Second, the generation process of alternating current.

in the power system.

and the rotating part ** sub) composition.

The stationary part is called the stator and is made of silicon steel sheets.

and coils to produce a uniform magnetic field. The rotating part is called the rotor and consists of a coil and a slip ring. The induced electromotive force produced by the coils on the rotor turning in a uniform magnetic field.

A slip ring is connected to the load to form an electric current.

Alternator model.

A coil that rotates in a magnetic field has two coil edges that cut the magnetic field lines.

These two coil edges are connected in series. Therefore, the strength of magnetic induction.

In a magnetic field that is b, the induced electromotive force of the rotating coil at time t is:

Induce electromotive force.

Induce electromotive force.

When t=0, e=0. When t = (1 4) t, e=em.

When t = (2 4) t, e = 0. When t = (3 4) t, e=-em.

When t=t, e=0.

From the above analysis, it can be seen that the coil rotates once in a magnetic field with only one pair of magnetic poles (one n pole and one S pole is called a pair of magnetic poles), and the induced electromotive force completes a change according to the sinusoidal law. The process of its repeated change is:

Starting from "0", it increases to the maximum value in the positive direction according to the sinusoidal law, and then decreases to "0" according to the sinusoidal law. Then increase from "0" to the maximum value in the opposite direction according to the sinusoidal law, and then decrease from the maximum value in the opposite direction to "0" according to the sinusoidal law.

Be. If the magnetic flux varies as a sinusoidal function, the alternating current emitted changes as a sinusoidal function. Because the electromotive force of power generation is proportional to the change in magnetic flux.

The magnetic field is a relativistic effect of the electric field, which is essentially an electric field force.

f=qe+qv*b

b=1/c2*v*e

where v is the velocity of the moving charge.

v is the velocity of the field source charge.

We call the force qe, which does not change with the change in the speed of motion, as the electric field force difference.

The force qv*b that changes with the speed of motion is called the electromagnetic force.

Under ideal conditions, the constant current virtual skin mill produces a constant magnetic field, and the changing current produces a changing magnetic field. A constant magnetic field does not produce an induced electromotive force, but a changing magnetic field will produce an induced electromotive force (whether it is a constant electromotive force or a variable electromotive force depends mainly on whether the rate of change of the magnetic field is constant).

A time-harmonic electromagnetic field is an electromagnetic field whose electromagnetic field changes sine or cosine with time. In time-harmonic electromagnetic fields, the complex representations of electric and magnetic fields have the following forms:

Electric field complex vector e = e0 * exp(i t) magnetic field complex vector b = b0 * exp(i t) where e0 and b0 are the positive amplitude of the cavity, are the angular frequency, t is the time, and i is the imaginary single-round position.

The definition of complex vector is to make it easier for Wu Tong to perform the operation of electric and magnetic fields. Through complex vector representation, you can directly use the properties of complex numbers for operation, eliminating the need to separate the real part and the imaginary part. In addition, the phase difference and phase relationship of electric and magnetic fields can be easily described by using the phase information of complex vectors.