Nowadays the wireless transmission system may seem very normal to us, however, centuries ago transmitting energy without physical contact could be called magic. But Nikola Tesla, the father of electromagnetism, knew perfectly well that with the necessary scientific knowledge, a wireless system could be generated and in fact, he did it with his famous Tesla coil. Much has been heard about this device with which the Serbian inventor demonstrated the power of electromagnetism to the world, but we are rarely explained how it actually works.
What is a Tesla coil?
Nikola Tesla dreamed of creating a way to supply electrical energy to the world without dependence on cables and in his invention process to pursue this concern, in 1891 he came up with his famous Tesla coil.
This was the first system with the ability to transmit electrical energy wirelessly and although today it is no longer in use, in its time it was positioned as one of the most revolutionary inventions. So much so that thanks to it the first radio and telegraphy antennas were created.
Although these have not been its only applications, as different variations of the experiment have led to creating lightning bolts, sending electromagnetic currents through the body, as well as creating electron winds.
The concept behind the Tesla coil may seem simple, but it is actually an invention that takes the most obvious characteristics of the fields and takes them to a very high level.
Constitution of a Tesla coil
The invention devised by Tesla consists mainly of two parts: a primary coil and a secondary coil, each with its own capacitor (devices capable of storing electrical energy also called capacitors). Both coils are different and are in turn connected by a spark gap, which is an air gap between two electrodes that generate the spark of electricity. It is fed with an external source connected to a transformer, which is what powers the entire system.
It could be said that the Tesla coil is made up of two open electrical circuits connected to a spark gap. But it is the characteristics of each circuit that make it possible to generate up to thousands of volts of output from a normal electrical supply.
The fundamental principles that govern the invention
To understand how the Tesla coil works, you must first understand the two fundamental principles of the electromagnetic force on which it is based: electromagnetic induction and magnetic resonance.
The first refers to the production of an induced voltage by exposing a coil to a variable electromagnetic field. That is, if we have a coil to which we apply an electric current, an electromagnetic field will be generated and in turn, if we use this variable electromagnetic field in a nearby coil, we can induce current to the second coil without having to apply current directly to it.
In that sense, a wireless transmission is already being generated but the problem with this principle consists of the distance at which both coils must be to generate induction. If they are separated by more than a few centimeters, the induction will lose strength and the second coil will stop producing electromagnetic current.
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For its part, resonance is a little more complicated to explain. This refers to physical excitation through magnetism and is carried out in resonant circuits that are composed of an inductor (coil) and a capacitor. Both elements have the property of storing energy, although they do it in a different way, the first through a magnetic field and the second with an electric field.
This type of circuit acts like an electrical resonator and to understand it we can use the example of a system composed of two tuning forks that generates sound waves. If we place both tuning forks separately, we can make the second vibrate by exciting the first, so when we make the first sound, the vibration waves will travel through the air and reach the second tuning fork which, as it is calibrated at the same frequency, will begin. to vibrate alone.
*Diagram of a resonant circuit.
The same thing happens with resonant circuits, if the capacitor is charged and connected in series to the inductor, in theory they could generate an indeterminate cyclic current, although in reality it does not happen this way because energy is lost due to electrical resistance. But Tesla used this type of circuits to amplify electrical currents just as the force of a swing is amplified:
If we activate a pendulum (or swing), it will begin to oscillate with a certain period that is lost. Over time the pendulum will stop oscillating as would the current passing through the resonant circuit. However, if the necessary force is applied to it at a certain point in the oscillation, we can make it begin to move more due to the sum of the forces, just as we do with swings to obtain a larger swing.
The same thing happens with the resonant circuits of the Tesla coil that use the apparently cyclical electrical current, and the configuration of its capacitors and inductors, to drive it and make it stronger.
How does the Tesla coil work?
The power supply is connected to the primary coil which is itself a resonant circuit, therefore it can convert normal power into a much higher current due to resonance. The power passes through the capacitor which eventually builds up so much electrical charge that it breaks the air resistance in the spark gap that acts like a switch, then the current leaves the capacitor and passes to the primary coil, generating a magnetic field that is as large that causes the electromagnetic induction of the second coil that is close to the first.
Voltage passes through the air between the two coils and moves back and forth between them several hundred times per second, building up in the secondary coil and its capacitor. But the charge in the secondary capacitor has grown so much through resonance that it is released in spectacular bursts of electrical current that characterize the Tesla coil.
The high-frequency voltage that rotates around the system is such that it can light fluorescent bulbs several meters away without the need for connection by cables. In short, Tesla’s great invention causes the primary bulb to constantly push the current through resonance and then through induction, a much higher current is generated than the initial one. Just like we push a swing at the right moment so that it swings harder and harder.