Inductionelectromagnetic it's the phenomenon responsible for the emergence of electric currents in materials conductors immersed in magnetic fields, when subject to changes in the magnetic field flux that crosses them.
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electromagnetic induction
Around 1820, Hans Christian Oersted found that there is a relationship between the phenomenaelectric and magnetic. Accidentally, Oersted noted that the passage of electric current on a conductor wire could change the direction of alignment of some compasses that had been left in the vicinity of the wire.
O experimentinOersted allowed us to understand that the electricity and magnetism, until then “independent” of each other, are phenomena of the same nature. It was from this discovery that studies on the electromagnetism.
According to advances in studies followed by the discovery of Oersted, it was understood that electric currents were capable of generating magnetic fields, the reciprocal, in turn, was only observed in 1831, when
Michael Faraday he discovered that an electric current was capable of producing a magnetic field. Therefore, faraday carried out several experiments, his experimental apparatus consisted of an iron ring wrapped in two windings (coils) of copper wires, connected to a drums and to a galvanometer (device used to measure current).
Faraday realized that when the battery was onorturned off, a current was formed in the galvanometer, however, this current ceased and only reappeared when the battery was connected or disconnected. Faraday carried out different experiments, in one of them he found that when a magnet towards a conducting coil (also known as a solenoid), an electrical current flows through it. He had discovered the principlegivesinductionelectromagnetic.
Michael Faraday had discovered that the movementrelative between a magnet and a coil was capable of producing an electrical current, currently this phenomenon is used worldwide, for the production of electricity in power plantshydroelectric plants, thermoelectric,nuclear,wind etc.
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Electromagnetic Induction and Faraday's Law
According to the lawinFaraday, when there is variationinflowinfieldmagnetic in some conductive circuit, like in a coil, a induced electromotive force (electrical voltage) arises in this conductor.
Flowmagnetic, in turn, it concerns the number of magnetic field lines that cross an area. That physical quantity, measured in Wb (Weber or T/m²), relates the intensity of the fieldmagnetic with the area and angle between the magnetic field lines and the normal line of the area.
Φ – magnetic flux (Wb or T/m²)
B – magnetic field (T – Tesla)
THE – area (m²)
θ – angle between B and the normal of area A
Although electromagnetic induction was a discovery of Faraday, he did not deduce it mathematically, nor could he explain the way in which the electromotive force emerged in the circuit, these implementations came later, at the hands of HeinrichLenz and FranzErnstNeumann, shaping Faraday's law as we know it today.
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Neumann's contribution concerns the equation of Faraday's law, he described it as a temporal variation of the magnetic field flux, see:
ε– induced electromotive force (V – Volts)
ΔΦ – magnetic flux variation (Wb)
t - time interval
The contribution of Lenz, in turn, it was related to the principle of energy conservation. Lenz explained what the direction of the electric current induced by the variation in magnetic flux must be. According to him, the electric current that is induced always arises in order to oppose the variation of external magnetic flux. Lenz's finding caused us to add the negative sign to Faraday's law:
The following figure shows how the induced electromotive force arises according to the Faraday-Lenz law, note that the lines of the induced magnetic field arise in order to compensate for the magnetic field flux variation which increases towards the interior of the solenoid:
Electromagnetic Induction Formulas
The main formulas for electromagnetic induction are the magnetic field flux formula and the Faraday-Lenz law, see:
Applications of electromagnetic induction
Let's get to know some direct applications of electromagnetic induction, including alternating current generators, transformers and electric motors.
alternating current generators
All generators of alternating electric current operate according to Faraday's electromagnetic induction. These generators are present in several types of power plants, and the common factor to all of them is that the electric energy is obtained from the conversion gives mechanical energy.
In hydroelectric plants, for example, the waterfall transforms the gravitational potential energy of a great mass of Water in kinetic energy, this energy produces the rotational movement of the generator blades, connected to powerful magnets and large conductive coils. If you are more interested in the topic, access our text: Generators.
Transformers
Transformers are devices that make direct use of the phenomenon of electromagnetic induction. These devices only work with alternating electrical currents and consist of an iron bar, usually in a U-shape, wrapped in two coils, with different numbers of turns. When electrical current passes through the first winding, a magnetic field is produced by the coil, which is then concentrated and transmitted through the iron bar. The second coil, exposed to the oscillating magnetic field, generates an induced magnetic field, contrary to that transmitted by the iron bar.
The difference between the numberinturns on each side of the iron bar makes the intensity of the induced electric current to be different in the two coils, however, the potency electrical current in each one of them is the same, thus, increasing the electrical current, there is a potential drop and vice versa.
This is how transformers operate: they can lower or lower the intensity of the electrical current according to the ratio between the number of windings in each of their coils. The formula used for transformers is shown below, check it out:
VP and Vs – primary and secondary voltages
NP and Ns – number of primary and secondary coil windings
Are you curious about this topic? Read our text: What is a Transformer?
Electric motors
You electric motors operate as inverted electric generators, that is, instead of converting mechanical energy into electricity, produce energymechanicsfrom electricity. In this case, instead of using the rotation of a shaft to generate electricity, we make an electric current pass through a shaft wound through several coils, causing it to rotate.
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By Me. Rafael Helerbrock
