"You look at this bar magnet, I tie a wire to the center of it, and I hang it in the air, and when it is still, I point to the south end, and I call it the south pole of the magnet, and the north end is called the north pole of the magnet. Then I put the north and south pole labels on both ends of it, and you also follow the steps I just took to mark the north and south poles of the other magnet! ”

In the Drunken Wind Xuan, Li Zexuan was carrying a bar magnet and was doing the most basic physical experiments for the four of them.

"Okay, let's try it too!"

Li Tai has read a lot of four books and five classics, but the real experiment has never been done, he just watched Li Zexuan play very happily on the side, he has long been gearing up, hungry and thirsty, at this time, when he heard the words, he immediately rushed up.

Li Zexuan smiled, let the little fat man play slowly by himself, he went to get two small pieces of paper, ready to put the magnet in his hand, pasted the "N" pole and "S" pole, suddenly stunned, this is in the Tang Dynasty, where did the ancients know "North" and "South", you mark a "N" and "S" who knows what it means?

In desperation, he shook his head, and could only write an "N" and "B" at both ends of the North and South Poles, just use the pinyin initials of South and North! Alas, what troubles! Many of the scientific terms and terms of later generations have various English abbreviations, how can this be done? Thinking of this, Li Zexuan couldn't help but feel a pain in his head, it seems that there is still a long way to go to improve Datang's scientific and technological level!

"Sir, Tai has also found the South Pole and the North Pole, huh~? Sir, what do you mean by this word? ”

Li Tai's hands-on ability was quite good, and it didn't take long to find the north and south poles of another magnet, but he looked at the two letters marked by Li Zexuan, and suddenly became a little puzzled.

"Qingque, do you remember pinyin? The N and B are the first letters of the pinyin of the south and the north, for the convenience of marking, we will use these two letters instead of the north and south poles in the future! ”

Li Zexuan couldn't help but feel glad for the wit just now, otherwise if he wrote an "N" and "S", how would he explain it.

"Oh~! I see, when Mr. said this, Tai also thought it was very convenient! ”

Li Tai was stunned, and then he did the same, marking the north and south poles of the magnet in his hand, at this time Li Zexuan took the two magnets in his hand, looked at the four of them, and said:

"Next, I want to tell you a very important theorem, that is, the poles of the same sex repel each other, and the poles of the opposite sex attract each other, if you don't believe it, you can try it yourself and see if this is the case!"

"Is there such a thing? I'll give it a try! ”

Li Yu took two magnets and started the experiment, although she didn't know pinyin, but whether the two letters were the same or not, she could still distinguish them.

"That's really the case! Sir, why is that? And what does this have to do with the compass being able to indicate directions? ”

After Li Yu played with the magnet twice, she tried the result predicted by Li Zexuan, and then she asked.

"Why do you repel sex and attract opposites, you think about this question slowly, of course, you can also understand him as the relationship between people, generally a man and a woman get married, you have never seen a man and a man or a woman and a woman get married, right?"

Li Zexuan couldn't explain this question clearly for a while, at that time, their physics teacher only said that this was a theorem, let everyone remember it, as for why in essence it is repelled by sex and opposites attract, how can he know, he can only drive without saying a word!

"Flutter!"

Li Yuwan smiled and said, "Sir's statement is really interesting!" ”

"Ahem, as for what this theorem has to do with the compass, I can only say that it has a lot to do with it. In fact, the earth can be seen as a large magnet, one of which is located near the geographic north pole, which can also be called the south pole of the geomagnetism, and the other pole is located near the geographical south pole, which is the north pole of the geomagnetism. According to the principle of same-sex repulsion and opposite-sex attraction, our magnets and magnetic needles can point to the north and south under certain conditions. ”

Li Zexuan began to popularize the knowledge of the geomagnetic field to them, and the eyes of several children widened when they heard such a novel theory for the first time.

"How is that possible? How can the earth we stand on be a magnet? ”

Li Tai muttered to himself, with a look of disbelief, this shocking remark simply subverted his worldview.

"Huh!"

Li Zexuan smiled and didn't say much, he walked to the vicinity of the next few cases and began to draw. A compass that is really used for navigation cannot be so crude and rudimentary, so untechnical.

In fact, in addition to the magnetic needle, the core part of the compass is its central axis, which should not only consider the balance of the needle, but also consider the friction when rotating.

Li Zexuan designed the shaft as a step shaft, drilled a hole slightly larger than the diameter of the thin end of the step shaft at the center of gravity of the magnetic needle, and tried to deform the end of the fine shaft after passing the magnetic needle into the fine shaft, and riveted the magnetic needle on the fine shaft to control the deformation of the fine shaft end and prevent the magnetic needle from being riveted. At this time, the magnetic needle can rotate around the fine axis without detaching from the fine axis. As for the cover of the compass dial, it can only be made of glass.

I used to be lazy and didn't make glass, but I didn't expect that I still can't get around the glass now, so this time I will make the glass by the way!

Thinking of this, Li Zexuan raised his head and ordered:

"Sanbao, go and invite Fu Bo over!"

"Yes, young master!"

Sanbao answered, and hurriedly ran out of the courtyard to find Fubo.

After a while, Fu Bo walked in and asked, "Young Master, are you looking for me?" ”

"Well, Fauber, let's see if this thing can be made."

Li Zexuan handed the drawings of each part of the compass to Fu Bo and said.

Fu Bo took it, looked at it carefully, pondered for a moment, and finally nodded, and said: "It should be possible, but it's very troublesome, young master, there are a lot of fine small parts in this thing you painted, if you want to make it exactly right, you have to do it yourself with those old craftsmen who are more than ten years old!" ”

When Li Zexuan heard this, he patted his head, and almost forgot that some of the components in this compass are almost equivalent to a small precision instrument, which is only a matter of seconds for the modern industrialized society with various lathes and machine tools, but it is really a big difficulty for the current situation of the ancient process that completely relies on pure manual polishing.

"Then Fubo, you organize a group of experienced old craftsmen as soon as possible, let them put down the work in their hands first, and concentrate on making a batch of compasses first, oh, I forgot to tell you, this thing is called a compass, which His Majesty is anxious to want, the imperial court This time the navy went south, mainly relying on this thing, discerning the direction in the vast sea, let the craftsmen hurry up, you make one more, maybe you will save the lives of a boatload of people at that time!"

Li Zexuan said with a serious expression, if there is a difficulty, it is difficult to serve the customer, although there is no modern process equipment in ancient times, but there are so many skilled craftsmen, many ancient handicrafts or buildings, modern people rely on machinery, and they can't be made.

Fu Bo thought that Li Zexuan came over today as before, purely to make some novel things for himself, but he didn't expect Li Zexuan to come with such an important task today, after listening to it, he hurriedly said:

"Young master, don't worry, up and down the workshop, we will definitely work together to make a batch of compasses in the next few days!"

…………………

First update!

Thank you A goodbye as before, love you is my only reward!

(End of chapter)