If you are studying electrical, circuit theory is the most fundamental and important lesson. If you can't learn it well, there is no way to learn about the later model, electric motor, power system analysis, and high voltage.
For this class, if you want to truly understand and master, the mystery lies in the inability to stop thinking. And I think this is the most important point. I take Jiang Jiguang's "Circuit Principles" as an example (this book is quite good) explaining why you can't stop thinking.
The circuit is almost the first book to start cultivating your engineers' thinking. It is different from mathematical physics, and many can be theoretically derived. And the circuit is more about your thinking and accumulated experience.
In Jiang's book, four chapters are used to explain the basic knowledge of the resistance circuit, including the reference direction problem, the substitution theorem, the branch method, the node voltage, the loop current, the Thevenin, the Telegen, and the Reciprocity Theorem. These basic contents must be mastered in order to be flexible in the following chapters.
How can I get used to it? I always remind myself to keep thinking. The after-school exercises of this set of textbooks are the best treasure trove of motivation for your brain. It can be said that every question inside is extremely targeted, and the topic is not difficult.
A qualified engineer should leave more time to think about how to solve the problem most reasonably, instead of spending a lot of time calculating, the calculation of the circuit is very large, a node voltage equation may be a quaternary equation, obviously These things are left to the calculator. In order to learn the circuit you should buy a Casio 991, saving those unnecessary waste of time to stay and think about the problem itself.
The foundation of the first four chapters must be played very solidly, not just staying on the line, and learning the circuit. You have to seriously study how each theorem comes from. It is best to prove it yourself. You must know that Thevenin is superimposed, and the superposition theorem does not come when the resistance circuit is linear. The theorem is derived from Telegen.
All this knowledge is accumulated by a little bit of water. You will feel confused when you first see them, but you have to believe that this is a process. Gradually you will feel that the circuit is wonderful and even loves it. When you find an answer that can be solved with a single page of paper, you can solve it with only five or six lines. At that time, you will feel that the circuit seems to flow out of your body. This is the realm that has always been pursued.
The latter is non-linear. Many of the requirements in this chapter are not high, and it is not difficult to test. It is very interesting to study it most.
Then there is the first-order second-order dynamic circuit. If you learn the high-order differential equation well, the high-level circuit knowledge can be solved. The essence of this part is to solve differential equations.
To put it bluntly, if you list the differential equations according to the circuit, you need to use the circuit knowledge. If you want to solve the problem, you can see your mathematics.
But the circuit teachers made a special topic for taking the first-order circuit alone in order to relieve the pressure on us, and summarized all the currents or voltages on the branches above it with a simple conclusion, that is, the three-element method.
I have learned the three-element first-order circuit and the equation is not listed. As long as you know the initial state, the end state, and the time constant of the circuit, you can get the result. If you are willing to think, in fact, the second-order circuit can also be analogous to it. In the second-order circuit, you only need to find the time constant, the initial value and the final value, as well as the general solution.
At the end of this section, I introduced a wonderful integral - convolution. Many people will be caught by his name and it will be very high-tech. In fact, it is really high-tech, but as long as you master the essence of it, you can use it well, and greatly improve your circuit thinking. There are many good explanations about convolution in Baidu and Baidu. A vivid example, I also learned from them.
I can only remind you here, don't ignore the convolution because the teacher doesn't focus on it, otherwise it will be like losing a sharp sword. I remember that when I was studying Du Amer's points (a type of convolution), I felt like a treasure, although there is only one sentence in the book. But for that sentence, my mood has not been calm for a long time, because it is so good.
Next is the sinusoidal circuit. Here is mainly to understand the transformation of the circuit from the time domain. Here is the first sublimation of the circuit. The great humans use their own wisdom to make a point on the exchange head, and then everything is calm. And then the knowledge of the first four chapters. I think he is using the same principle, all the quantities are changing at a frequency, the effect is more like static, but they have a new impact on the capacitance and inductance, because they There is a differential and integral relationship between the current and voltage. In the new idea, you can turn the inductor into jwl and turn the capacitor into 1/jwc. Then you can think about why it can be changed.
This is derived from the current-voltage relationship at polar coordinates. You have to trace back to the source, why can you use the plural instead of the sine? That's because the Euler formula transforms the sine into a plural expression. What else do you ask Euler's formula? It is derived from the McLaughlin (Taylor) formula. You must constantly think and keep asking questions to understand what is going on here.
However, this is the basis. The essence of sinusoidal steady state is to draw a vector diagram. You can correctly draw a vector diagram and you can really understand it. The vector map is not a doodle. It is not that you can find the correct map after you have found a branch. If you go wrong, you won't get the correct answer. Instead, you may fall into the spiral of thought. The vector diagram generally takes a resistance branch or a branch containing a resistor as a horizontal vector, and then pushes it step by step according to its current and voltage. And many problems are hiding a lot of information in the picture, you can't figure out a good picture. This also requires you to figure out.
Behind the mutual feelings, I believe that many people are killed by the same name. In fact, the inductance is the amount of the ability of the coil to establish a magnetic field. The inductance is large and the magnetic field is generated. Therefore, the meaning of the same name means: the current flowing from the same name end, the magnetic field is added, and the equation is added to the inductance. Just keep this in mind, and the equations that contain mutual inductance are not wrong. Don't think about it, sometimes you will be confused by the direction of the current, leave it alone, the picture is drawn on the reference direction, even if your hypothetical direction is opposite to the actual direction, there is still no effect on the true result. Here is actually to examine your understanding of the direction of reference.
Then there is resonance, which is a very interesting and useful section, whether it is electrical, communication, mode or high voltage. This is a perfect transition between power plant energy and position energy in a wonderful state. Circuits with practical significance such as filtering and boosting can be realized by resonance. However, as far as the circuit content is concerned, it is not difficult. To sum up, the imaginary part of the impedance is zero and the series resonance, and the imaginary part of the admittance is zero. When solving the resonant frequency, it is sometimes convenient to use the admittance solution, which is to open up the idea.
Next is the three-phase circuit. For me, the three-phase circuit is the simplest part. Many people find it difficult (of course I also feel dizzy at first), simply because we are always afraid of fear itself. In fact, you see that it has three places but it is not difficult at all. It takes your mind to be clear and not to be scared by his face. The three-phase circuit is no different from the ordinary circuit. Doing five or six power supplies will not be scared, because you know that a circuit that all components are telling, using node voltage or loop current is certainly achievable.
Why are you scared when you get to the three phases? Do you understand the relationship between line voltage and phase current, or the effect of one-phase disconnection on the neutral current? What do you care about? What is the line, it is just a code name. You see it as a normal circuit solution, it is just a normal circuit. Many students always like to tangled in the relationship between online and related. In fact, one sentence can be summarized: the line quantity is three times the root of the vector. In fact, these do not need to remember, when you need to draw a picture will come.
The most important thing is that you have to understand that the three-phase is just a normal circuit with three power supplies. As long as you will have the node voltage method, you can answer the three-phase knowledge well. When you look at it in a normal circuit, the three phases have already learned almost. The only difficulty in the three-phase is calculation. As long as you are a careful person, you usually find a few more questions to calculate. It is difficult to think about the three phases in the future.
Followed by the Laplace transform. Here is another leap in circuit thinking. It has been found that high-order circuits are really difficult to solve, and if the power supply changes, there is no better way than convolution. So in order to use convolution conveniently, the predecessors introduced the Laplace transform into the circuit. If the front sinusoidal steady state time domain to the frequency domain is step by step from the Taylor formula. That is the last chapter of the high number - the Fourier transform was overthrown. There are also many wonderful explanations about Fourier, and I will find it myself.
There are two forms of Fourier transform, one is the time domain form and the other is the frequency domain form. The Laplace transform is to extend the Fourier transform from the frequency domain to the complex frequency domain. The basic transformation formula is also generalized by the Fourier transform formula. In this chapter of learning, you should start with the transformation formula and derive the basic transformations yourself. It is also necessary to understand the final value theorem and the initial value theorem. These two theorems are strong evidence for the correctness of the test results.
Learning circuit only knows that thinking is one thing, and being able to do it is another matter. Only by cultivating your broad vision and powerful computing skills in your studies can you learn this course well. It is hard work to learn the circuit. When you look at the teacher's problem solving, you feel that you are convinced, but you are puzzled. That is, Kung Fu is not in place.
When I was in the postgraduate examination, I saw the circuit for about a hundred days. The new books were ruined, and my old books were falling apart. The exercises were done at least 1,500 times without repeating. When I was doing the circuit, I felt that time had stopped, and I couldn’t feel anyone else in the study room. The kind of happiness that brings you a laugh after finally solving a problem after contemplating is the best medicine to accompany me. Walking in the moonlight every day, I will think, if you can't be a scientist, do something else.
So, ah, to learn the circuit, you still have to love it from the heart.
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