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A Few years ago among some students and fans of physics the idea of an independent development of questions in this exciting field of knowledge. Was organized a circle of "Lovers of physics." In our circle often had hot disputes on a variety of topics from the field of physics. Was no particular order in these questions. However, once we had remembered the debate, which is against our will, sent the conversation in the direction of a system. We are not noticed for 6 months repeated, and with what pleasure, almost the entire main course of electricity. Our fierce debate started with the fact that someone of the friends said,
, finally, unbearable... You keep saying like a parrot: all bodies electrified by friction, and I tell you now, I aelectricity any subject, to walking in our room, you won't be able to do, and now will be a lengthy and confusing to explain why all existing items "generally speaking electrified, but in our situation to make such an experience impossible." Impossible, and not crucified on universal electrification. After the attack our President pushed to his candle, and said,
— And I, my dear, don't know why you attacked us. And you know perfectly well that every body, rubbed about anything, electrified. But one thing is electrified strongly, the other — is weaker, the third is so weak that rude ways to detect therein the presence of electric charge is absolutely impossible. Surely you didn't get enough of all these experiences? Glass rubbed on the skin — it is electrified; the ebony stick on the carpet — it also electrified. And the newspaper didn't we rubbed ? Finally, even each other, we were electrified — beat me on the back of his fur cap, and my thumb was attracted small pieces of paper ?!
"Ah," replied our debater, I very well know myself, but know that all these experiments require special equipment and materials, and I say that if you convince others that all bodies electrified by friction, so ought to use this item, which is available in household and electrification that does not require a number of tweaks. We rubbed the glass skin, but the skin was covered with amalgam (to cover the leather used most often tin-zinc amalgam, i.e., an alloy of tin and zinc with mercury. Amalgam generally called a solution of metal in mercury). Rubbed ebonite stick, but in what house there are sticks ? We have electrified the newspaper, but you probably forgot what we were waiting for a whole week of dry days and in the end had but to drink the stove in order to dry and heat the sheet of newspaper. Moreover, when the room had accumulated to ten people to enjoy the spectacle of electrification "our press", as you put it then this is the "press", with the furious rubbing of her brushes, gave at first some results and then from the breath of the audience was damp and staged a "mass strike". Well, the last experience wonderful. And people everywhere there, and a fur hat can take, but in order to be able to electrify you, you had to stand on an isolated bench, or the electricity you would have gone to the floor, and from it the walls of the house into the ground. Maybe you will say that and insulating the bench to get one in every home?
— You're bitter, ' said our Chairman.— But only you did wrong. First things first; the skin does not have to amalgamate — amalgam is used to enhance the electrification. You won't find anywhere but in a physical office; this, of course, not; but who's stopping you to replace the ebonite well, at least, for example, of wax or celluloid? As for the experiments with newsprint sheet with the electrification of the person, from his point of view you're probably right, but...
Debater interrupted the Chairman:
— I did not ask whether I am right or not. You give me immediately electrifying. That's what I'm asking.
Well, well, ladies, ' said the Chairman. Only this time according to our rules the ladies — as a challenge to you.
Problem # 1
the candle and the pieces of newspaper
— Prove it with the help of this candle, — said the Chairman — that it can be electrified. Here's another piece of newspaper.
— clear To me, — said our indomitable friend, what would you suggest a piece of paper only to use it as a body, attracted to the candle. But tell me, please, how I can electrify it if you don't want me to RUB it. — Because I do not give, — said the President, — that you have something you can RUB a candle. And I have, and all our friends there, and indeed all people, with very few exceptions. Well, to solve the problem; nothing more to say.
Enough stearic candle two or three times to hold the hair, or RUB it on a cloth clothes for her electric. To detect the charge on the candle can be a variety of techniques. Every electrified body has the property to attract very light bodies. Of course, if the electric charge is very weak, we may not be able to detect gross ways, but more sophisticated devices (for example, electroscope) will allow you to install the electrification of the body.
Pick a few small pieces of newspaper, going to offer him electrified end of the candle, they are immediately attracted. — Wait, — said one of those present, I want to suggest another task. Of course, we now know very well that nepovadno (insulators) of electricity, strictly speaking, does not exist. All of the body — and silk, and glass, and porcelain, and other so-called insulators — to a greater or lesser extent carried out through electricity. However, this quantity of electricity is so slight that for practical purposes it is possible to neglect the conductivity of insulators. I want to say, comrades, that we continue to divide all bodies into conductors of electricity— metals, solutions of salts, acids, alkalis, and not conductors of tar, oil, etc.. I Say all this in order that you not find fault with my
Problem # 2
All on the same candle
How, without any experience, in addition to proposed in problem number 1, we can prove that stearin is a very good insulator? If you did experience specified in the task number 1, you probably noticed how long holds charge of the stearic candle. A sign of a good insulator. Indeed, stearin great insulator. This is evident already from the fact that you, holding the candle at one end, was able to electrify the other. If the stearin was a conductor, then you would not be able to keep it on charge, like electricity through your hand would have gone into the ground.
Well, this task is simple — someone said of us, — but my share this summer had that I still can't let you. I began to tell to one man in the village that lightning is supposedly the electric discharge to "jump—tell him—the electricity from the clouds to the earth." Told him everything I knew. "The closer," I said. " some object to the cloud, and the better he is the conductor, the more likely it will get zip. That is why,—tell him—lightning hits so often in the belfry". He looked at me and said,
Problem # 3
the Riddle of man
Fig. 1. Our Church is over 40 years old, and never in her cross got struck by lightning
— our Church is already more than 40 years, and never in her cross was struck by lightning. But, boy, during these 40 years, the storm burned in our village, one mill, two houses, people beat the crap out of pozhnya, Scott, I don't remember them all. What is far to remember—I have a very under the day of Elijah, the haystack burned this year. Here's the bell tower! I told him that maybe the Church stands in a deep hollow, and a haystack on the hill. Grandpa laughed: "Yes you that, our Church is not seen, or what?! The Church is on thin ice, brother, is worth. The highest point in our village — stone and sand. A stack of mine, read that the wetlands were."
That was my answer, comrades? After about a bell-I had read in books, and then life itself.- Bad was that the old man was obviously implied that the cross on the Church and "Malonga" do not touch. I'm not glad that started this conversation. — Yes, Yes, ' said the other one of us, I myself was witness to a similar case.
Problem # 4
I Lived in the high Bank of the Ob river near the Biysk. This beach near my house formed a deep beam, the bottom of which ran a spring. Just in front grew two trees: pine upstairs, downstairs high aspen. During a thunderstorm lightning hit in aspen and heavily splintered and mutilated her and the pine tree, whose top was raised much higher than aspen, remained intact. You see, comrades, that's the same case. These two tasks are strongly interested us.
Especially for the fact that we at first didn't even know how to accept their decision.
lightning Strikes are very diverse and whimsical. Often find the causes of lightning in this place is absolutely not possible in the absence of accurate information about all the conditions of the environment, which was at the moment of impact. Question about lightning not once discussed in our circle, and the reader will receive information about atmospheric electricity. However, the question posed in this problem can be solved pretty simple reasons," the Cloud aims to transfer its charge into the ground. Because air is a very bad conductor, the charge clouds with a strong accumulation of electricity punches him in the form of a giant spark that we call lightning. Obviously, this category chooses the path having the least resistance to the passage of electricity. The resistance of the air is not everywhere the same. It depends on the greater or lesser concentrations of water vapor, the water in the form of tiny droplets, dust, etc. Therefore, the path of the lightning is very rarely direct. If we stick upright in the ground a long wooden pole, and he during a thunderstorm is soaked with rain, you will get a much better conductor than air. The higher will be the pole, the more likely a lightning strike will be directed at him.
great importance in the question of the place of the lightning plays and the properties of the surface of the earth itself. A thick layer of completely dry sand or clay is a very good insulator. On the contrary, the wet black earth strip is a good conductor.
Thus, we are interested in the matter shall be resolved just. The Church stood on a hill of sand and stone. Therefore, even if we assume that the Church itself from the top of the cross to the Foundation and was a satisfactory or even a good guide, yet she could not give lightning a path to earth, devoid of much resistance, as the Church was the formation of the insulator. On the contrary, the haystack, although it was below the Church, stood, in the words of farmer, "on wetlands". The perfect conductivity of the ground and conductivity of the hay, moistened stormy rain, could easily create the conditions under which the path of lightning into the ground via a stack differed less resistance than through the Church. The last question of problem you can easily solve yourself, based on the same considerations, which we led in the previous. It should be noted that there mixed and one more thing: deciduous trees ceteris paribus have better conductivity than conifers.
Maybe you will be able to point to one reason for such properties of deciduous trees? The next day, when problems were solved, our debater has shared with us another loss.
— I rubbed a candle with a piece of cloth — candle electric, as it attracted bits of paper. It was obvious to me that if it is true the rule that all bodies electrified by friction of any other body, if only it wasn't with him of the same material, and soukenka should alectrosaurus. However, my experiments led to the following.
Problem # 5
neelektrizuyuscheysya the cloth
Rubbing a cloth on a candle, I brought it not only to the pieces of paper, but even by the end of the hanging sewing threads and could not find the slightest trace of electricity. Maybe on the cloth appears from the friction of the candle, the charge is much weaker than the candle, which can only be detected by very sensitive instruments? This problem will be solved instantly. All bodies electrified by friction to a greater or lesser extent. Hence it is clear that the cloth due to the friction of the candle must alectrosaurus. At friction of two bodies one on the other both electrified heterogeneous electricity. Stearin candles, rubbed on cloth, is electrified negatively, hence the cloth must receive a positive charge.
Finally, the experience and theory to convince us that the quantity of electricity on both friction bodies is the same. Therefore, the assumption that the cloth obtained charge less than the candle, is fundamentally wrong. The whole question is resolved very easily if we remember that the cloth is though a very bad conductor, but a conductor of electricity. Holding it in your hand, we're taking the electricity into the ground. If we fastened it to any insulator, for example, to the second candle, we would have discovered on the cloth a positive charge, exactly equal to the negative of the candle. We put it on the form of our friend, which he obviously badly acquired electricity, if you offered us such a task.
okay, Okay, — he said, — we all know that I'm worse you know electricity. And here I will tell you about my invention that I did yesterday.
Challenge No. 6
Imagine that the middle of the room hanging from the ceiling, a metal ball, which is all the time highly charged with electricity. You know flies always hover around a hanging lamp; it is clear that they will curl around the ball. Due to the fact that it is electrified, the force will be drawn to him, and to fly with him can not. Powys, Powys and die. Laughter greeted this original project.
— You are we talking. — Flies not only will not stick to the ball, and even if they wanted to stay on the surface, so they would dump her. The ball will attract a fly, it is true, but as soon as the fly touches the ball, she charged it with electricity. And you very well should know that like charges of electricity repel each other. Now, if you somehow managed to charge a fly, say, negative, then of course. the fly is attracted to the ball as long as it' and on the ball would be heterogeneous electricity. But how would you have it implemented in practice? Because the fly will inevitably touch the ball, and then may be three things. If the ball of electricity was the same as in the fly, these two equal and opposite quantities of electricity are mutually neytralizuya: all the power of one and the other mutually annihilated. Then your fly will just fall on the floor. If the charge on the ball is greater than on the fly, that part of it which is equal to the charge flies will neutralize it.
the Rest of the electricity spread around the globe and partly going to fly, will push her away from the ball. Also happens if the remaining flies will be more charge of the ball. Proposed by the inventor of the flytrap is theoretically feasible. However, if we covered a metal ball with a layer of nonconductive, for example, selcom, then obviously, then the charge of the ball couldn't go to fly, and she would be under the influence of gravity. Practically, this Flycatcher is, of course, are so uncomfortable and the road (after all, the electrification of the ball need a special device, which was charging him) that no one would think to use it for catching flies.
— Look, — said the inventor of flycatchers, who this time will be the winner. I know that like charges of elektrichestva repel, and unlike attract. You are to me now give an answer to know that if any body of, say, strings, pieces of paper, straws, etc. will be attracted to the electrified body, after convenia they should proceed or not?
— Clear need, — said the Chairman, that in any book.
— In the book I'm not watching, but you enjoy better in my experience. So I rubbed a candle on my hair, rubbed the wax on the carpet. Now mind if I pick some pieces of paper. Look!
On the pieces of paper that undermines the laws of electricity
If you bring an electrified candle or a stick of sealing wax to the pieces of paper, these pieces are attracted to him, but, against expectations, did not repel after it touches, but continue indefinitely to stay on the surface. Why is this happening?
We were stunned by this experience. Undoubtedly, this time defeated our friend. However, what's going on here? After all, our reasoning was undoubtedly correct, and experience specified in problem No. 7, also did not cause the slightest suspicion. This problem we could not solve. When we have accumulated enough experience and knowledge, we finally understood the mysterious cause of the strange behavior of paper. The reader at the time also know about it from this book. It was decided to postpone the solution of this problem and first determine the justice of the basic laws of the interaction of electricity. One of us is here suggested on this subject
Task No. 8
Again on the candle
— Here, comrades, I put on the table a candle and a spool of thread. Prove that the same electricity repel each other.
— Wait to decide, said second member of the circle, I immediately and the second task the ladies.
Problem # 9
in addition to candles and a reel of thread, take a glass tube and a piece of leather and prove that the opposite electricity attract each other.
We tried to solve the first problem thus: hung close two sewing thread and then electrified them with a candle. It is obvious that both lines in this case had to alectrosaurus the same (negative) and therefore repel each other. However, the experience was disappointing. Both lines, prijanovici to the candle, were reluctant to let her go, and we realized that in this case we came across some mysterious phenomenon, which was mentioned in problem number 7. From here we could draw only one conclusion: either we have solved this problem in the wrong way, or our friend, who offered it to us, gave an impossible task. Some of us even said he could solve this problem and otherwise if were given two candles.
— One I'd hang on a thread, strengthening it in the middle so that the candle was in a horizontal position. Then I electrified one end of this candle and the second. The second candle would be closer to the electrified end of the suspended. Both candles would be electrified with the same electricity, the end of the suspended candles would be a start. This idea is suggested to us the solution of the problem. Who prevented us from one candle to make two? We broke our candle in half and convinced, finally, that charges of the same, in any case, negative, repel each other.
After solving this problem the second seemed to us quite simple. Glass tube rubbed on the skin, we got on it a charge of positive electricity. Bringing it to the dangling candle (pre-electric), we found the attraction of its end to the vacuum tube glass. The attraction of the opposite electricity has been proven. These experiences we are very diversified: hung instead of candle lamp glass and even against the terms of this task, took the second glass and therefore, made sure that between the positive charges there is a repulsion. The question of the interaction of electricity was understood.
"Comrades," I said, ' today and I can please you with my discovery, although it is not experimental in nature. Have you heard ever about how in France in the middle ages was revealed to electricity?
"No," said my comrades.
Objective # 10
As a French scientist has gone mad
Fig. 2. He had done absolutely incomprehensible manipulation c black and white stocking
it was in Paris. I do not know what it was century, but back then all wore long stockings and short pants. One French scientist was hastily invited on a business trip to the French king. To report to the court ought in white silk stockings, and the scientist was a silk black.
Angry that he tore off from work, and not wanting to waste time on dressing up, the scientist began to pull the white stocking black. Stockings stretched with great difficulty. The scientist hastily pulled the stocking up to the heel. Irritated, he began pulling off the white stocking with the black, but to his surprise, could not seem to do it: one stocking as if stuck to another. Completely mad, he jerked with all my strength down and pulled with his feet both socks at once. Came into a rage, he threw them against the wall. Stockings stuck to the wall and fell to the floor. All annoyance was instantly forgotten, and the scientist, amazed by the unusual behavior of the stockings, forgetting about the Royal order, began to explore this phenomenon. When the hour arrived the king sent a second time to pass that the king's wrath, they were thrown into the greatest confusion the picture that presented itself to their eyes. The scientist was sitting in a chair. His one foot was in a black stocking, the other bare. He had done absolutely incomprehensible manipulations with black and white stockings: he then rubbed them together, then run into one another. Sent told his master that the scientist has gone mad. And a happy scientist and did not go to the Palace. That's the whole story. In it, I immediately noticed the absurdity. We know that static electricity from the friction of only two heterogeneous bodies, and in this story two electrified silk stockings. Obviously, that's impossible.
you Can imagine my surprise when our Chairman proved to me that I'm wrong.
— it is Clear that silk, worn on silk, should not electrified, — the President said, — but you yourself said that the main condition for the two bodies in friction against each other is not electric is not in the fact that both bodies were of the same material, and that they were perfectly homogeneous (most importantly, their friction surfaces). Take, for example, glass. Let us be two pieces of the same class, but if the surface is one to scratch the skin * and then rubbing them against each other, they will get electrified. exactly. In order to obtain the electrification of two bodies of the same material, just one of them to heat up or compress. From the heated body surface will be less dense than that of not heated; compressed, on the contrary, more dense. This is sufficient to ensure that the surfaces of these two bodies was not homogenous. White silk is pure silk. Black — the silk is dyed. This is enough for the friction of them one on the other, they are electric. So, you see, you're wrong, and nothing did the opening. And here I am, listening to your legend about the discovery of electricity, it seems, can offer you all permission...
Excerpt from the book by V. Sieber "mystery of electricity"
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