Today we will reveal such a phenomenon of physics as the "law of electromagnetic induction." We will explain why Faraday conducted the 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 man is afraid of the abyss of the sea and the distance of space. But science can explain why. Submarines record the incredible life of oceans over a kilometer deep, space telescopes study objects that existed only millions of years after the big bang.
But then people deified everything that fascinated and disturbed them:
- Sunrise;
- awakening of plants in the spring;
- rain;
- birth and death.
In every subject and phenomenon, unknown forces lived that ruled the world. Until now, children tend to humanize furniture and toys. Left unattended by adults, they fantasize: a blanket hugs, a stool fits, the window opens by itself.
Perhaps the first evolutionary step of mankind was the ability to maintain fire. Anthropologists suggest that the earliest bonfires were lit from a tree that was struck by lightning.
Thus, electricity played a huge role in human life. The first lightning gave an impetus to the development of culture, the basic law of electromagnetic induction brought mankind to a modern state.
From vinegar to a nuclear reactor
Strange ceramic vessels were found in the Cheops pyramid: the neck was sealed with wax, and a metal cylinder was hidden in the depths. On the inner side of the walls found the remains of vinegar or sour wine. Scientists came to the 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 investigated. The fact that amber gives categories, if rubbed on fur, the ancient Greeks knew. The color of this stone reminded them of the light of the star Electra from the Pleiades. And the name of the mineral, in turn, became the reason to christen the physical phenomenon.
The first primitive direct current source was built in 1800
Naturally, as soon as a sufficiently powerful capacitor appeared, scientists began to study the properties of the conductor connected to it. In 1820, Danish scientist Hans Christian Oersted discovered that a magnetic needle deflected next to a conductor connected to 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 extract electricity from water, wind and nuclear fuel.
Primitive but modern
The physical basis of the experiments of Max Faraday was laid by Oersted. If the included conductor affects the magnet, then the reverse is also true: a magnetized conductor should cause current.
The structure of the experiment, which helped to deduce the law of electromagnetic induction (EMF as a concept, we will consider a little later), was very simple. The wire coiled into the spring is connected to a device that registers current. The scientist brought a large magnet to the turns. While the magnet was moving near the circuit, the device registered the flow of electrons.
Since then, the technique has improved, but the basic principle of creating electricity at huge stations is still the same: a moving magnet excites current in a spring-wound conductor.
Idea development
The very first experience convinced Faraday that the electric and magnetic fields are interconnected. But it was necessary to find out exactly how. Is there also a magnetic field around the conductor with current, or are they simply capable of influencing each other? Therefore, the scientist went further. He coiled one wire, brought a current to it, and pushed this coil into another spring. And also received electricity. This experience proved that moving electrons create not only an electric, but also a magnetic field. Later, scientists found out how they are located in space relative to each other. The electromagnetic field is also the reason why light exists.
Experimenting with different options for the interaction of live conductors, Faraday found out: the current is transmitted best 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.
Formula and its components
Now that the story of the study of electricity has been brought to the Faraday experiment, it's time to write the formula:
ε = -dΦ / dt.
Decrypt:
ε is an electromotive force (abbreviated as EMF). Depending on the value of ε, the electrons move in the conductor more intensively or more weakly. EMF is affected by the power of the source, and electromagnetic field strength affects it.
Φ is the magnitude of the magnetic flux that is currently passing through a given area. Faraday rolled the wire into a spring, since he needed a certain space through which the conductor would pass. Of course, it would be possible to make a very thick conductor, but it would be expensive. The scientist chose the shape of a circle because this flat figure has the largest ratio of surface 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 circular cross section is much easier to obtain: it is enough to wind the wire around a round object.
t is the time during which the stream passed through the circuit.
The prefix d in the formula of the law of electromagnetic induction means that the quantity is differential. That is, a small magnetic flux must be differentiated over small periods of time in order to obtain the final result. This mathematical action requires some preparedness from people. To better understand the formula, we strongly encourage the reader to recall differentiation and integration.
Law Consequences
Immediately after the discovery of Faraday, physicists began to study the phenomenon of electromagnetic induction. Lenz’s law, for example, was experimentally derived by a Russian scientist. It is this rule that added a minus to the final formula.
He looks like this: the direction of the induction current is not accidental; the electron flow in the second winding, as it were, seeks to reduce the action of the current in the first winding. That is, the occurrence of electromagnetic induction is actually the resistance of the second spring to interference with “personal life”.
The Lenz rule has another consequence.
- if the current in the first coil increases, then the current of the second spring will also tend to increase;
- if the current in the induction winding drops, then the current in the second decreases.
According to this rule, the conductor in which the induced current occurs actually seeks to compensate for the effect of the changing magnetic flux.
Grain and Donkey
People have long sought to use the simplest mechanisms for their own benefit. Grinding flour is a difficult matter. Some tribes grind grain by hand: put wheat on one stone, cover it with another flat and round stone, and twirl the millstones. But if it is necessary to grind flour on a whole village, then one can not do without muscular labor. At first, people guessed to tie a draft animal to a millstone. The donkey pulled the rope - the stone was spinning. Then, probably, people thought: “The river flows all the time, it pushes all kinds of objects downstream. Why don't we use it for good? ” So there were water mills.
Wheel, water, wind
Of course, the first engineers who built these structures did not know anything about the force of gravity, because of which water tends to always go down, nor about the friction force or surface tension. But they saw: if you put a wheel with blades on a diameter in a stream or a river, it will not only rotate, but also be able to do useful work.
But this mechanism was also limited: there is not always running water with enough current flow. Therefore, people went further. They built windmills.
Coal, fuel oil, gasoline
When scientists understood the principle of excitation of electricity, the technical task was set: to receive it on an industrial scale. At that time (mid-nineteenth century), the world was in a fever of cars. They sought to entrust all the complex work to an expanding couple.
But then they knew how to heat large volumes of water only with fossil fuels - coal and fuel oil. Therefore, those regions of the world that were rich in ancient carbon, immediately attracted the attention of investors and workers. And the redistribution of people led to the industrial revolution.
Holland and Texas
However, this state of things has a bad impact on the environment. And scientists thought: how to get energy without destroying nature? Rescued well forgotten old. The mill used torque to carry out direct rough mechanical work. Hydroelectric turbines rotate magnets.
At the moment, the cleanest electricity is derived from wind power. The engineers who built the first Texas generators relied on the experience of Holland windmills.