Today we will reveal such a phenomenon of physics as the "law of electromagnetic induction". We will tell you why Faraday conducted experiments, give a formula and explain the importance of the phenomenon for everyday life.
Ancient gods and physics
Ancient people worshiped the unknown. And now a man is afraid of the depths of the sea and the distance of space. But science can explain why. Submarines capture the incredible life of the oceans at a depth of more than a kilometer, space telescopes study objects that existed only a few million years after the big bang.
But then people deified everything that fascinated and disturbed them:
- sunrise;
- awakening plants in spring;
- rain;
- birth and death.
In every object and phenomenon lived unknown forces that ruled the world. Until now, children tend to humanize furniture and toys. Left unattended by adults, they fantasize: a blanket will hug, a stool will fit, the window will open by itself.
Perhaps the first evolutionary step of mankind was the ability to maintainthe fire. Anthropologists suggest that the earliest fires were lit from a tree struck by lightning.
Thus, electricity has played a huge role in the life of mankind. The first lightning gave impetus to the development of culture, the basic law of electromagnetic induction brought humanity to the present state.
From vinegar to nuclear reactor
Strange ceramic vessels were found in the pyramid of Cheops: the neck is sealed with wax, a metal cylinder is hidden in the depths. Remains of vinegar or sour wine were found on the inside of the walls. Scientists have come to a sensational conclusion: this artifact is a battery, a source of electricity.
But until 1600 no one undertook to study this phenomenon. Before moving electrons, the nature of static electricity was explored. The ancient Greeks knew that amber gives discharges if it is rubbed against fur. The color of this stone reminded them of the light of the star Electra from the Pleiades. And the name of the mineral became, in turn, the reason to christen the physical phenomenon.
The first primitive DC source was built in 1800
Of course, as soon as a sufficiently powerful capacitor appeared, scientists began to study the properties of the conductor connected to it. In 1820, the Danish scientist Hans Christian Oersted discovered that a magnetic needle deviated next to a conductor included in the network. This fact gave impetus to the discovery of the law of electromagnetic induction by Faraday (the formula will be given below), which allowed mankind to extractelectricity from water, wind and nuclear fuel.
Primitive but modern
The physical basis of Max Faraday's experiments was laid by Oersted. If a switched conductor affects a magnet, then the opposite is also true: a magnetized conductor must induce a current.
The structure of the experience, which helped to derive the law of electromagnetic induction (EMF as a concept, we will consider a little later), was very simple. A wire wound into a spring is connected to a device that registers the current. The scientist brought a large magnet to the coils. While the magnet was moving next to the circuit, the device registered the flow of electrons.
The technique has improved since then, but the basic principle of creating electricity at huge stations is still the same: a moving magnet excites a current in a conductor wound by a spring.
Idea Development
The very first experience convinced Faraday that electric and magnetic fields are interconnected. But it was necessary to find out exactly how. Does a magnetic field also arise around a current-carrying conductor, or are they simply able to influence each other? Therefore, the scientist went further. He wound one wire, brought current to it, and pushed this coil into another spring. And he also got electricity. This experiment proved that moving electrons create not only an electric field, but also a magnetic field. Later, scientists figured out how they are located in space relative to each other. The electromagnetic field is also the reason why there islight.
Experimenting with different options for the interaction of live conductors, Faraday found out that the current is best transmitted if both the first and second coils are wound on one common metal core. The formula expressing the law of electromagnetic induction was derived on this device.
The formula and its components
Now that the history of the study of electricity has been brought to the Faraday experiment, it's time to write the formula:
ε=-dΦ / dt.
Decipher:
ε is the electromotive force (EMF for short). Depending on the value of ε, the electrons move more intensively or weaker in the conductor. The power of the source affects the EMF, and the strength of the electromagnetic field affects it.
Φ – the magnitude of the magnetic flux that is currently passing through a given area. Faraday coiled the wire into a spring, because he needed a certain space through which the conductor would pass. Of course, it would be possible to make a very thick conductor, but that would be expensive. The scientist chose the circle shape because this flat figure has the largest ratio of area to surface length. This is the most energy efficient form. Therefore, water droplets on a flat surface become round. In addition, a spring with a round section is much easier to obtain: you just need to wind the wire around some kind of round object.
t is the time it took the flow to pass through the loop.
The prefix d in the formula of the law of electromagnetic induction means that the value is differential. I.ea small magnetic flux must be differentiated over small time intervals in order to obtain the final result. This mathematical action requires some preparation from people. To better understand the formula, we strongly encourage the reader to recall differentiation and integration.
Consequences of the law
Immediately after Faraday's discovery, physicists began to investigate the phenomenon of electromagnetic induction. Lenz's law, for example, was experimentally derived by a Russian scientist. It was this rule that added a minus to the final formula.
He looks like this: the direction of the induction current is not accidental; the flow of electrons in the second winding, as it were, tends to reduce the effect of the current in the first winding. That is, the occurrence of electromagnetic induction is actually the resistance of the second spring to interference in "personal life".
Lenz's rule has another consequence.
- if the current in the first coil will increase, then the current of the second spring will also tend to increase;
- if the current in the inducing winding drops, the current in the second winding will also decrease.
According to this rule, a conductor in which an induced current occurs actually tends to compensate for the changing magnetic flux.
Grain and donkey
Use the simplest mechanisms for their own benefit, people have been striving for a long time. Grinding flour is hard work. Some tribes grind grain by hand: put wheat on one stone, cover with another flat and round stone, and twirlmillstone. But if you need to grind flour for an entire village, then you can’t do it with muscular labor alone. At first, people guessed to tie a draft animal to the millstone. The donkey pulled the rope - the stone rotated. Then, probably, people thought: “The river flows all the time, it pushes all kinds of things downstream. Why don't we use it for good? This is how water mills appeared.
Wheel, water, wind
Of course, the first engineers who built these structures did not know anything about the force of gravity, due to which water always tends to fall, nor about the force of friction or surface tension. But they saw: if you put a wheel with blades on a diameter in a stream or river, then it will not only rotate, but also be able to do useful work.
But even this mechanism was limited: not everywhere there is running water with enough current strength. So people moved on. They built mills that were powered by the wind.
Coal, fuel oil, gasoline
When scientists understood the principle of excitation of electricity, a technical task was set: to obtain it on an industrial scale. At that time (mid-nineteenth century) the world was in a fever of machines. They tried to entrust all the difficult work to the expanding pair.
But then only fossil fuels, coal and fuel oil, were able to heat large volumes of water. Therefore, those regions of the world that were rich in ancient carbons immediately attracted the attention of investors and workers. And the redistribution of people led to the industrial revolution.
Holland andTexas
However, this state of affairs had a bad effect on the environment. And scientists thought: how to get energy without destroying nature? Rescued well forgotten old. The mill used torque to do directly rough mechanical work. Turbines of hydroelectric power plants rotate magnets.
Currently, the cleanest electricity comes from wind power. The engineers who built the first generators in Texas drew on the experience of windmills in Holland.
