Junior high school physics involves the knowledge of voltage, resistance and current, and in order to enable students to better transition from theory to practice, some of the practice questions are related to transformers. Pen & Fun & Pavilion www.biquge.info

It was from this aspect that Liu Fang learned the basic working principle of the transformer, and in order to ensure safety, he carefully picked up a dead branch and turned the switch down.

Then Liu Fang picked up the thread and got busy in the dark: "This is the zero line...... This is the line of fire...... This is the ground ......"

In less than five minutes, Liu Fang connected the wire, he struck a match and checked it to make sure that he did not have any omissions, and then turned the switch back on the transformer with a dead branch, because it was late at night, Liu Fang's behavior was not noticed by anyone.

"That's all set, now all we have to do is go back and give it a try."

Liu Fang walked quickly towards the station, and a quarter of an hour later, he returned to his home in the wilderness.

After Liu Fang entered the house, he first lit the kerosene lamp, and in the dim light, Liu Fang removed a few abandoned wires from the wall and tied them to the plug of the radio equipment.

Then he bent the other end of the wire into a hook, carried this end with a bamboo pole and walked out of the door, relying on his own impression, hooking the end of the wire to the wire.

After doing all this, Liu Fang walked into the inner room, hesitated for a while, and then pressed the power switch on the radio device.

In order to better meet the communication needs of the military, the Soviets increased the power of this equipment, so that it can increase the frequency range of receiving and transmitting radio waves, and even in very bad weather conditions, it can still carry out long-distance communication work without hindrance.

"Zizi-zi-zi-" After turning on the device, Liu Fang immediately heard a chaotic zizi sound.

"What the Soviets made is leather, and after so many years, it can still be used normally, and the next thing to do is to adjust the signal reception frequency and see if there is any gain."

With excitement, Liu Fang began to adjust the receiving frequency of this military radio station according to the knowledge he had mastered.

"Zizi-zi-"

After adjusting for a while, there was always a sizzling sound in the device, and until Liu Fang tried all the frequencies of this device, he didn't hear any sound except for the sizzling sound, which made Liu Fang's originally excited mood immediately cold.

The transmission of military signals is generally encrypted, and only the radio equipment with a specific decoder installed can restore this information, but this does not mean that military equipment cannot receive other forms of radio signals, the equipment in front of Liu Fang has the function of receiving other signals, but if no one sends a signal in the relevant frequency band, this equipment is completely a decoration.

finally carried out the actual operation, but did not achieve any results, which made Liu Fang have a deep sense of loss, fortunately, he was not a person who gave up easily, and not long after being lost, Liu Fang made a second attempt.

The result was still nothing, and Liu Fang made a third attempt, then a fourth, then a fifth......

After ten failures in a row, Liu Fang finally accepted the reality, he sat on the ground dejectedly, and began to think about the cause of the problem.

"It's military equipment, and it's much tougher than ordinary civilian equipment. But I've been debugging for so long, why can't I receive the signal? ”

Military radio stations generally use ultra-short wave as the communication frequency, compared with other bands, ultra-short wave has better stability, and more long communication distance, it is no exaggeration to say, as long as the military radio station is turned on, and the power is adjusted to the maximum, you can basically receive all the signals sent by the world's high-power short-wave radio, such as the BC radio station in the United Kingdom, or the voice of the United States on the other side of the Pacific Ocean, can be heard.

It is precisely because of this that Liu Fang is very puzzled by the performance of this military radio, there can be absolutely no problems with the technology of the Soviets, people can even build an atomic bomb, what is the difficulty of a military radio station?

"Something must have gone wrong, but I didn't find it, so what went wrong?"

Liu Fang got up and began to circle around the military radio, and as he walked, he said to himself: "Well, the signal light shows that everything is normal, is there something wrong with the signal receiver?" ”

Liu Fang squatted down when he said this, carefully checked the signal receiving end, and did not find anything abnormal, just as he was about to stand up, his brain was short of oxygen because of the lack of blood supply after squatting for a long time, and Liu Fang couldn't help but feel dizzy. He hurriedly reached out to hold the radio, but only to touch something sharp in his palm.

Liu Fang got used to it for a moment, then opened his eyes and took a look, and at a glance, Liu Fang slapped his head suddenly: "Liu Fang, Liu Fang, you are really stupid, such an obvious link, why did you miss it?" After doing so much for a long time, it turned out that the antenna was not pulled out! ”

In an instant, Liu Fang's face showed excitement again, and he hurriedly stretched out the antenna and found that the telescopic antenna was about one meter long.

After the antenna was stretched out, the sizzling sound from the radio station became louder, Liu Fang was not the slightest unhappy, he put on the headphones, and adjusted the receiving frequency again.

It didn't take long for Liu Fang to receive the radio signal, and the host's soft voice came from the headphones: "Hello listeners, this is xx radio station, let's enter the "Storytelling World" column of this station, and we will play the storytelling "Romance of the Sui and Tang Dynasties" for everyone." ”

This was the first time Liu Fang had heard a radio program in his life, and he immediately pricked up his ears and listened attentively.

It is said that the eighteenth road anti-king gathered 2.3 million troops at the foot of Siping Mountain...... That Li Yuanba held a drum urn and a golden hammer, urging the smoke and clouds under his crotch to come to the front of the battle...... In just one round, the purple gold stick in the hand of Luo Tiehan, the king of Shatuo, was blown out, Luo Tiehan was so frightened that his face was pale, he just turned the horse's head and was about to flee to the team, Li Yuanba's right hand sledgehammer smashed down with the wind, smashing Luo Tiehan's brain...... NX King Ma Delai held a flaming snake spear and stabbed Li Yuanba...... In an instant, five of the eighteen anti-kings died...... Li Yuanba was like a tiger entering a flock of sheep, rushing left and right in the crowd, no one could stop him, and he only killed the eighteen-way anti-king army, and the 2.3 million army was wiped out......"

At the beginning, Liu Fang felt that this Li Yuanba was really powerful, he was simply a god-like figure, and later heard that Li Yuanba had defeated an army of 2.3 million alone, Liu Fang really couldn't listen to it, he pouted: "Do you think Li Yuanba is an atomic bomb?" Isn't it that one person can win against an army of 2.3 million alone? ”