What Zhu Cijiong wanted Xu Fuyuan and Xia Yunyi to learn was the law of electromagnetic induction, so that after they had a preliminary understanding of electricity, this magnetism would naturally be demonstrated, and a small experiment he was going to conduct next was to use iron powder to demonstrate magnetic field lines.

At this time, Xu Fuyuan and Xia Yunyi were already shocked in their hearts, they had already vaguely understood that what the emperor wanted them to do was probably related to thunder and lightning, it was thunder and lightning above the nine heavens, and it was trembling to think about.

They trembled Zhu Cijiong did not tremble, he calmly commanded a group of eunuchs to continue the experimental course, and then he took a thick square plank, two feet square, the thickness is about two inches, square, smooth and flat, it is a piece of fine wood.

Although the plank is good, it is not the point, the point is that there are two rectangular grooves on the board, about two fingers thick, about an inch apart, what is this for, why should a good plank be cut out of two slots?

The answer was soon revealed, and two more eunuchs came up with two elaborate wooden plates, on which were placed two long black stones, the size of which were embedded in the grooves of the planks.

Zhu Cijiong picked up a black stone with one hand, let the back two hands slowly approach, there was a soft 'snap', the two stones stuck together, and he asked with hope: "Do you know what this is?" ”

This is not a novelty, it is just two magnets, Xu Fuyuan and Xia Yunyi have naturally seen it, you look at me, I look at you, they are embarrassed to answer, and in the end, Xu Fuyuan repeatedly humbled with his eyes, Xia Yunyi nodded and said: "If you go back to the emperor, we know that this is a magnet." ”

Now that he knew, he didn't have to bother to explain, Zhu Cijiong broke the two magnets, stuffed them into the groove of the wooden board, and then gestured like Cao Huachun.

Cao Huachun gave a soft order, and immediately two more eunuchs came up with a delicate wooden plate, but this time the things that came up were a little strange, it turned out to be a stack of thick cardboard with a white surface and a glass bottle with black powder, what is this for?

Zhu Cijiong didn't let them guess, as soon as the thing came up, he immediately took a piece of cardboard and put it on the table, then picked up the glass bottle, sprinkled the powder inside evenly on the cardboard, and explained while sprinkling: "This is filled with iron powder, so you can take a closer look at it next." ”

After he sprinkled the iron powder, he immediately covered the cardboard on the wooden board, the size was just right, the cardboard and the wooden board were tightly fitted together, as if they were a whole, of course, this is not the point, the next is the point.

Zhu Cijiong flicked his fingers lightly on the cardboard, and a magical scene appeared, the iron powder on the cardboard slowly began to line up into a regular pattern, where the magnets below were two dense black squares, and the other places showed evenly spaced arcs, and the arcs in the middle of the two magnets also blended together, forming a complete arc.

Xu Fuyuan and Xia Yunyi looked at all this in amazement, it was amazing, what the hell was going on?

Zhu Cijiong continued to explain: "The magnet is also called a magnet, and there are invisible magnetic field lines around the magnet, which are born with the magnet, you don't need to understand how it came about, just know that there is this thing, you can try it first." ”

With that, he gently picked up the cardboard, put it aside, and then picked up the glass bottle on the table and stuffed it into Xu Fuyuan's hand.

Xu Fuyuan is still very interested in this novel 'experiment', and now since the emperor asked him to do it, he didn't twist it, he directly took the glass bottle respectfully, followed Zhu Cijiong's example, took a clean cardboard, sprinkled the iron powder evenly on the cardboard, and then covered the cardboard on the wooden board, and gently flicked it with his fingers.

The iron powder slowly gathered, forming a pattern similar to that just now, Zhu Cijiong nodded and said: "Well, yes, I look very seriously, and I learn very similarly, you stand back first." ”

Xu Fuyuan won the emperor's praise, and stood back, his nervous mood was relieved.

Next, Zhu Cijiong gently put aside the cardboard used by Xu Fuyuan, then pulled out a magnet and stuffed it back in a reverse direction, and then said to Xia Yunyi: "Yi Zhong, you can try it too." ”

Xia Yunyi was already eager to try, and when he heard this, he immediately couldn't wait to step forward and take a clean piece of cardboard, follow Zhu Cijiong's example, pick up the glass bottle and sprinkle the iron powder evenly on the cardboard, and then cover the cardboard on the wooden board, and gently bounce it up with his fingers.

The pattern formed this time is different from the previous two, the arc where the two magnets intersect is actually staggered from each other, did you do something wrong? Xia Yunyi puffed out his eyes and looked at the magnetic field lines on the cardboard and froze.

Zhu Cijiong stepped forward kindly, picked up the cardboard and put it aside, then pulled out the two magnets inside, stuffed them into Xia Yunyi's two hands, and explained with a smile: "Yi Zhong, you haven't done anything wrong, this magnet is polar, the same pole repels each other, and the opposite pole attracts, you can just try it." ”

Xia Yunyi breathed a sigh of relief when he heard this, he was really shocked just now, it was not a joke to do something wrong in front of the emperor, it would be a loss of favor, and a loss of head, but fortunately he didn't do anything wrong.

He settled down, slowly approached the two magnets in his hand, and sure enough, he felt a mutually exclusive force, and he followed Zhu Cijiong's example, turned the magnet upside down, and then slowly approached, with a soft sound, the two magnets stuck together.

At that time in the Ming Dynasty, even if he saw a single magnet, even if he was well-informed, who would be bored to find two magnets to suck ah, for a while, Xia Yunyi felt novel, holding two magnets and constantly turning around, all kinds of directions, all kinds of angles, approaching again and again, playing happily, and Xu Fu on the side looked at it from afar.

Seeing this, Zhu Cijiong couldn't help but shake his head and smiled: "Okay, I have asked the Ministry of Industry to collect a lot of this thing, you can go back and ask Chang Geng for a few pieces to play, Yi Zhong, you put the magnet back, and we will continue to the next experiment." ”

When Xia Yunyi heard this, his old face turned red with shame, and he quickly stuffed the two magnets back into the wooden trough, and then respectfully stepped aside.

Zhu Cijiong signaled to Cao Huachun again, and then two more eunuchs came in, but this time the experiment was a bit big, and they came in with a large wooden plate.

How to describe the thing that was brought up this time, it is simply a thick wooden board and a hand-spun wheel. There were also two grooves in the thick plank, but they were obviously not magnets, but ordinary pieces of iron; The wheel used for hand-spinning is also incomplete, only a round wooden pole in the middle, no spinning wheel, and a magnet is tied to the wooden pole.

The two eunuchs put the things on the long table and respectfully retreated, Zhu Cijiong stepped forward to operate it himself, he first took out two pieces of iron and demonstrated them to Xu Fuyuan and Xia Yunyi, even if they were placed very close, there was no sign of mutual attraction, and then he said: "This is an ordinary piece of iron, not a magnet, you can try it." ”

After that, he stuffed the two pieces of iron into Xu Fuyuan's hand, Xu Fuyuan took the two pieces of iron and tried them a few times, and sure enough, they were two ordinary pieces of iron, which had no magnetism at all, and after trying, he respectfully returned the pieces of iron to Zhu Cijiong.

Zhu Cijiong took the pieces of iron, stuffed them back into the wooden trough, then took a clean piece of cardboard, sprinkled some iron powder evenly, and then covered the cardboard on the board, and gently flicked it with his fingers, but the iron powder on the cardboard naturally did not move at all.

Zhu Cijiong did not stop there, but put the cardboard aside, buckled out an iron block, then picked up a long thin gold wire in the wooden plate, carefully wrapped it around the iron block a few times, and then stuffed the iron back into the wooden trough, and then he wound the fine gold wire under the spinning wheel, arranged it into a rough ring, and twisted the two ends of the gold wire together.

After doing all this, he clapped his hands and said mysteriously: "Next, you have to look carefully, this is the point I asked you to learn today." ”

That thin golden silk Xu Fuyuan and Xia Yunyi naturally saw it a long time ago, they thought it was for decoration, and it was also used for 'experiments' for a long time, but now the emperor let them look at it carefully, and he naturally puffed out his eyes and stared at the emperor's hands seriously.

I saw Zhu Cijiong gently cover the cardboard sprinkled with iron powder back onto the wooden board containing the iron block, and then grabbed the rotating handle of the spinning wheel and turned it vigorously.

A magical scene appeared again, the iron powder on the cardboard slowly gathered towards the iron block around the gold thread, and soon formed a regular long bar above the iron block, Zhu Cijiong said while shaking the handle: "Fu Zhai stepped forward to play the cardboard, just like just now." ”

Hearing this, Xu Fuyuan hurriedly stepped forward and gently flicked the cardboard, and there were the same magnetic field lines on the cardboard as just now, but there was only around the iron block with the gold wire, and there was still no movement above the iron block that did not have the gold wire.

At this time, Zhu Cijiong stopped turning his wheel and said solemnly: "You remember, this is the point I asked you to learn, now I will explain it to you, you may not understand, but you must remember, keep it in your heart, and slowly understand, one day you will understand." ”

Then, he pointed to the thin gold filament and said: "This is a filament made of gold, gold, silver, copper, iron and other things actually have a commonality, that is, they can all conduct electricity, I give them a name, they are called metals, and those with similar properties to gold are called metals, you remember that metals have a commonality, that is, they can conduct electricity." ”

Then, he pointed to the magnet on the wheel and said: "This is the magnet, also called the magnet, you also saw it just now, there are magnetic field lines around the magnet that cannot be seen by the naked eye." ”

Finally, he pointed to the magnetic field line pattern on the cardboard that he had just taken off, and said solemnly in a majestic tone: "I have done so many tests to let you understand that when the loop formed by the metal does the movement of cutting the magnetic inductance line, electricity will be generated in the metal loop, and if the charged metal wire is wound into a coil, it will produce magnetic force, which is the same magnetic force as magnet, that is to say, electricity and magnetism can coexist!" ”

Well, it's metal, it's loops, it's electricity or something, there are too many fresh terms, and the average ancient person will probably listen to them in the clouds, but Xu Fuyuan and Xia Yunyi are not ordinary people, they are quick thinkers, they are logical, they are the kind of geniuses who study science, plus Zhu Cijiong gave them a series of experiments to demonstrate. They really understand the principle of electromagnetic symbiosis!