The method of generating a steady current, and discussing its significance and function.

The above god said that the relationship between steady current and uniform motion, this analogy is very good, the generation of steady current, taking electromagnetic generators as an example, the current generated by the generator is related to the movement speed of the coil and the angle between the speed direction of the coil and the direction of the magnetic field, when the speed of the coil is constant, and the angle between the direction and the direction of the magnetic field is also constant, the current generated is the steady current, and the other method is through the synthesis of related circuits, this principle can be understood by Fourier series, To put it simply, the periodic function can be decomposed into functions of various frequencies (generally trigonometric functions), so some sinusoidal signals of a specific frequency can be synthesized into the desired output current signal (steady current) according to a certain weight, and this method is more used in electronic circuits (analog circuits). I can't say much about the meaning for the time being, for example, when we first came into contact with the knowledge of circuits, we all used the knowledge of direct current to speak, indicating that it is simple in principle and easy to control, but the earliest application circuits (transmission of electric energy) are all used in direct current, and later after the theory of alternating current is proposed, it is slowly used to distribute and transmit electric energy, which shows the advantages of alternating current compared with direct current, flexible control, low loss, good safety and other characteristics.

A constant current that exists inside a conductor and does not change in magnitude with time is called a constant current.

Constant current. The magnitude and direction of the current intensity at each point in the current field do not change with time.

For the steady current circuit, although there is the loss of electric heat and magnetic energy, that is, there is the problem of energy conversion, but because the steady power supply, conductor and charge carrier that constitute the steady current circuit constitute the same system, the interaction force between them belongs to the internal force, and such a system is not affected by other external forces, therefore, the conditions required by the law of conservation of momentum are met, so that the momentum of the steady current is conserved.

Steady condition of this paragraph A circuit with a constant current must be closed - the current through any enclosed surface is zero.

Several conclusions can be drawn from the steady condition: The conductor surface current density vector cannot be directed to the component.

For a steady circuit with no branches.

The current intensity of each of its cross-sections is equal.

At any node of the circuit.

The sum of the incoming currents is equal to the sum of the currents outgoing nodes.

When designing the shape of the electrode, it is necessary to enlarge or shrink the electrode according to the shape, size and distribution of the charged body in the electrical equipment.

Both Gauss's theorem and the loop theorem (described in Maxwell's equations describe the properties of the electric field) must be satisfied. This can be achieved by the circuit continuity equation as long as it is a constant current.

The potential of the steady current field satisfies the same Laplace equation as the potential of the electrostatic field (see Poisson and Laplace's equations), and the solutions of the equations are similar when they have similar boundaries. Therefore, the electrostatic field can be simulated with a steady current field, which is a common method for experimental study of electrostatic field.

Having a high-voltage generator will do the trick. Choosing more than 1 million volts can basically achieve many test purposes.

The relationship between the allisome and the power line is always perpendicular. Requirements: 1. Both Gauss's theorem and the loop theorem (the description of the properties of the electric field in Maxwell's equations) must be satisfied.

2. If the electrostatic field in the air is simulated, the conductive medium used should be a conductive medium with uniform resistance and isotropic conductive materials as the current field. 3. The shape of the electrode should be used.

Maxwell said that a uniformly varying electric field produces a constant magnetic field, but it is not a uniformly varying electric current that produces a constant magnetic field. Direct current is not a uniformly varying electric current, but a uniformly varying electric field.

Because a stable current can be regarded as an electron moving uniformly, then the electric field naturally changes uniformly, so the current can produce a laughing magnetic field while a constant electric field does not produce a magnetic field, and the electric field of a constant current is uniform.

Due to the action of a constant electric field, the rate of directional motion of free charges in a conductor increases; In the process of motion, it collides with the immobile particles inside the conductor and decelerates, so the average rate of the free charge does not change with time.

Ampere's Law (Ampere'S law) is the law of magnetic interaction between electric currents, discovered by Ampère in 1820, and is one of the fundamental laws of electromagnetism.

In a steady magnetic field, the linear integral of the magnetic induction intensity b along any closed path is equal to the algebraic sum of the individual currents enclosed by that closed path multiplied by the permeability. This conclusion is called the Ampere Circuital Theorem. The Ampere's loop theorem can be derived from Bio Savall's law.

It reflects the interconnected nature of the magnetic induction wires and current-carrying wires of a steady magnetic field.

In the plane perpendicular to the long direct current-carrying wire, make an arbitrary loop l as shown in the following figure around the current-carrying straight wire, and take the circumambulation direction of the loop as the counterclockwise direction.

Select a point p in the middle of the solenoid with a long direct current in the hand, and symmetrically select two turns of circular current on both sides of point p, and it can be seen from the magnetic field distribution of the circular current that the direction of the magnetic inductance b is parallel to the axis direction of the solenoid.

In a steady current magnetic field in a vacuum, the linear integral of the magnetic induction intensity b along the arbitrary closed curve l (also known as the circulation of the b vector) is equal to the algebraic sum of all the current intensities passing through the closed curve, i.e., the intensity of the electric Sun current passing through any surface bounded by the closed curve.

DC power supply principle: The electric field generated by the positive charge alone cannot maintain a constant current, but with the help of DC power supply, a non-electrostatic action can be used (so that the positive charge returns to the positive electrode with a higher potential difference from the negative electrode with a lower potential difference through the switching power supply, so as to maintain a two-level potential difference, and then generate a constant current. A DC power supply is a device that maintains a constant voltage and current in a circuit.

The non-electrostatic force in a DC power supply is deflected from the negative to the positive. When the DC power supply is connected to the external circuit, the current flowing from the positive electrode to the negative electrode will be generated outside the switching power supply (external circuit) due to the impetus of the electric field force. In a switching power supply (internal circuit), the action of the non-electrostatic force causes the current to flow from the negative electrode to the positive electrode, which in turn causes the flow of the positive charge to produce a closed circulation system.

One of the characteristics of the switching power supply itself is the electromotive force of the switching power supply, which is equivalent to the work done by the non-electrostatic force when the positive power of the enterprise moves from the negative electrode to the positive electrode according to the switching power supply. When the internal resistance of the switching power supply is negligible, the electromotive force of the switching power supply can be felt to be numerically similar to the potential difference or working voltage on both sides of the switching power supply.

The current of the ideal electric branch current source is always a constant number of constant values, independent of the voltage at its parade end. （）

a.That's right. b.Mistake.

Correct Answer: True.

No. If the constant voltage source (U) is connected in series with the constant current source (i), and then the resistor (R) is connected, and the three constitute a loop, then:

The constant current source controls the current of the whole circuit, and the power of the bridging and resistor elimination bucket is actually controlled by ir.

If U>IR, the constant current source is equivalent to a resistor (internal resistance) and consumes power instead of output power;

U=IR+U (U is the voltage consumed on the constant current source).

If UU R, then the constant voltage source is equivalent to a resistance (internal resistance) that consumes power rather than output power;

i=u r+i (i is the current drawn on the constant voltage source, in reverse).

If ii+i = u r (i is the current output on the constant voltage source, forward).

If i=u r, then the constant voltage source does not take effect (internal resistance), and the current is all output by the constant current source, and the current i on the constant voltage source line is zero.

1. Its internal resistance is infinite, that is, the voltage drop on it is determined by the external side, which can be approximated as infinite power;

2. Its output current does not change with the external load, that is, the external load has no influence on it, and it can still maintain a constant current output even if it is short-circuited, instead of becoming an infinite current;

3. Due to these characteristics, the constant current source is generally regarded as an open circuit.

4. In reality, there is almost no similar constant current source, some chips can form a constant current circuit, and the negative feedback loop composed of op amps can achieve an approximate constant current, but the general current value is small, less than 1A, and other devices are required to cooperate with amplification to achieve the constant current of a larger current.