Today we will talk about the experience of Faraday, an English physicist, and the importance of electromagnetic induction in the modern world.
Sun, lightning, volcano
Ancient people worshiped the obscure. We are talking about the times when the most advanced invention was the ability to combine a stick and a stone into a simple tool. There was no explanation for the daily course of the Sun, the phases of the Moon, volcanoes, the occurrence of lightning and thunder.
With thunderstorms, mankind has a separate affair. The fire dispelled darkness, gave a sense of security, inspired discovery. And scientists suggest that the first guided bonfire was created from a tree set on fire by lightning.
Hammer and magnet
A little later, people learned to use heat to melt metal. The first strong tools appeared that helped to conquer the surrounding nature. Going exclusively by experimental means, various masters must have stumbled upon unusual and strange incidents. For example, one piece of iron could suddenly begin to move in the presence of another (magnetism). In the nineteenth century, these phenomena were explained by the experiments of Faraday (electromagnetic induction in the modern sense arose precisely then).
Science and Kings
Electric current has been known for a long time. They knew how to distinguish iron from glass by the property of conducting electrons in the days of Michelangelo. But until the beginning of the nineteenth century, this phenomenon was considered exclusively as a fun phenomenon. In addition, scientists have always been sponsored by a wealthy philanthropist - count, duke or king. And the money invested, as you know, should have paid off. So physicists and chemists needed to work in such a way that the military power of the noble was strengthened, he made big profits or enjoyed the spectacular sight.
Some experiments were demonstrated to guests as a sign of the power of the owner of the money. Galileo named the satellites of Jupiter discovered by him in honor of his patron Medici. So it was with electricity. The experiments of Faraday electromagnetic induction confirmed experimentally. But before him were the studies of Oersted.
Electric or magnetic?
The magnet (the main part of the compass) was used by sailors who discovered America, Australia and the way to India. Electricity was fun. In 1820, Danish scientist Hans Christian Oersted proved the connection of the magnetic and electrical properties of conductors. His experiment was a precursor to the experience of Faraday, the phenomenon of electromagnetic induction and all that followed from the discoveries of those years.
So, Oersted took a linear conductor (thick wire) and placed a magnetic needle under it. When the scientist started the current, the poles of the magnet shifted: the arrow stood perpendicular to the conductor. The physicist repeated the experiment many times, changed the geometry of the experiment and the direction of the current in the conductor. The result was the same: the location of the poles of the magnetic needle was always the same with respect to the electron motion vector. Now this experience seems very simple and understandable. But the discovery had far-reaching consequences: Oersted proved the direct connection of electric and magnetic fields.
Property Relationship
But since the electric current was able to influence the magnet, then the magnet could cause the movement of electrons? That is what Faraday tried to prove by experience, the description of which we will now give.
The scientist wrapped the wire in a spiral (coil), connected a current-recording device to it and brought the magnet to the structure. The meter needle flinched. The experience was successful. Subsequently, Michael Faraday used a variety of approaches and found out: if instead of a magnet one takes a coil and excites current in it, then a current will also appear in the adjacent coil. The interaction is even more effective when a conductive core is inserted inside the turns of both spirals.
The law of electromagnetic induction
The Faraday law of induction for a closed loop is expressed by the formula: ε = -dΦ / dt.
Here ε is the electromotive force that causes the electrons to move in the conductor (abbreviated as EMF), Φ is the magnitude of the magnetic flux that is currently passing through a given area, and t is time.
This formula is differential. Therefore, the EMF should be calculated for all small segments of time for small pieces of area. And in order to get the full electromotive force, the result must be summed up.
The minus in the formula is due to the Lenz rule. It reads: EMF induction is directed so that the excited current blocks the change in direction of flow.
To explain this rule with an example is quite easy: with increasing current in the first coil, the current of the second will also increase; when the current in the first coil decreases, the induced one will also weaken.
Application of Faraday Law
Modern life cannot be imagined without electricity. In the film “The Day the Earth Stood Still”, the character Keanu Reeves changes the course of human history by turning off the generators. We will not talk about the mechanisms of this incident. Fiction gives vent to imagination, but does not describe the possibilities. But the consequences of such a phenomenon would be truly global: from the destruction of urban infrastructure to hunger. People would actually have to rebuild civilization in order to adapt to an existence without electricity.
Many science fiction writers exploit the plot of a global catastrophe. In addition to blackouts, the reasons for such serious changes are:
- foreign invasion;
- incorrectly conducted bacteriological experiment;
- accidental discovery of a physical law that changes the structure of matter (for example, ice-9);
- nuclear war or disaster;
- the evolutionary leap of people (new humanity just does not need technology).
The search for energy sources is a separate area of human activity. People use the energy of fossil resources, water, wind, waves, the heat of underground thermal water and the atom to get electricity. All stations operate thanks to the principle, the existence of which Faraday proved in his experiments. Moreover, the scheme for generating electricity is not too different from his experiment: a certain force rotates a huge magnet (rotor), and that, in turn, excites current in the coils.
Of course, people found excellent material for the cores, learned how to make huge bobbins, and they insulated the winding layers much better from each other. But in general, modern civilization is based on the experience made by Michael Faraday in August 1831.