LAW OF ELECTROMAGNETIC INDUCTION OF FARADAY AND ITS APPLICATIONS

The electromagnetic induction discovered by Faraday is one of the most important events in physics. Its innumerable applications gave beginning to the technologies that in the modern era we know. Television, telephony, satellites, motors, power generators, voltage transformers, the distribution of electricity from hydroelectric power stations, etc. would not be possible without Faraday's legacy.

Faraday inspired by the works of Hans Christian Orsted, who demonstrated that an electric current generate a magnetic field, he considered the possibility that a magnetic field generated an electric current. What he demonstrated successfully in 1831 after years of research work.

In one of his experiments he observed that a variable magnetic field generated by the relative motion between a magnet and a coil was capable of deflecting the needle of a galvanometer.

Figure 1 -Effect of magnetic flux variation
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Figura 2
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The results of their work were conclusive:

The variation of a magnetic flux is capable of inducing an electromotive force

Figure 3
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The negative sign in Faraday's law is introduced by Heinrich Friedrich Emil Lenz to explain the polarity changes of the induced voltage.

Lenz's Law

The currents that are induced in a circuit are produced in such a way that their magnetic effects tend to oppose the cause that originated them.

According to Faraday's law, we can induce tension with just the creation of a variable magnetic flow.

Since the magnetic flux by definition is the amount of magnetic field that crosses a certain surface, a voltage can be induced if any of these parameters or both vary in time.

In the following circuit it can be observed that if the sliding bar moves on the rails or if the magnetic flux density "B" varies in time a current will be induced in the circuit generating a voltage in the resistance.

Figure 4 - Example of Electromotive Force
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This is a surprising fact, since we can generate or induce a voltage without having a real voltage source.

Voltage transformers and speakers are other important applications of Faraday's law.

Figure 5
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Figure 6
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Figure 7
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It should be noted that if the power supply of the devices shown is a "DC" source, the direct current generated by said source would produce a constant magnetic field and therefore a magnetic flux with the same characteristics, resulting in the voltage induced is null.

Thanks to Faraday's work, Maxwell formulates his first equation, which is written in the form.

Figure 8
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Other contributions of Faraday are known, such as electrolysis, the Faraday cage with its applications in aeronautics and microwave isolation.

Undoubtedly his contribution on the electromagnetic induction is his legacy of greater importance.

References

• Griffiths, David (2012). Introduction to Electrodynamics (4th ed.).

• Purcell, Edward Mills (1985). Electricity and Magnetism. McGraw-Hill.

• Teoria Electromagnetica. 7E. Hayt, Buck.

• Tipler, Paul; Mosca, Gene (2007). Physics for Scientists and Engineers. 2 (6th ed.). W. H. Freeman.

• Ulaby, Fawwaz T. (2007). Fundamentals of Applied Electromagnetics (5th ed.). Pearson Education.