The principles behind the Tesla coil are relatively easy and simple. We know that electrical current is the flow of electrons, while the difference in electric potential or voltage between two places is a kind of force that pushes the electrons (current). In simple terms, the current is like water and voltage is like a hill. A high voltage is a steep hill, down which a stream of electrons can rapidly flow whereas a small voltage is like a nearly flat plain with almost no or slightly water flow.
Tesla coil works on the principle of electromagnetic induction. According to this principle, a changing magnetic field creates a voltage that compels the current to flow. In a turn of the coil, the generated electric current generates another magnetic field. And this process goes on continuously till the power losses completely. When electricity flows through a wound-up coil of wire, it generates a magnetic field that fills the area around the coil in a particular pattern.
In the same way, this principle also says, if a magnetic field flows through the center of the coiled wire, a voltage is generated in the wire, which causes an electric current to flow. This generated voltage increases with the number of turns of wire. For example, a changing magnetic field within a coil of 100 turns will generate ten times the voltage of a coil of just 10 turns.
A power transformer works on the same principle. Tesla coils also do the same thing but in a different way. Let’s understand this, suppose a premade high voltage iron core transformer to go from 110V wall current to roughly 10,000V. The wire with 10,000V is wrapped into the primary coil. The secondary coil contains thousands of turns of thin wire. This steps up the voltage to 1000,000V. This voltage is so strong that can destroy the iron core. To handle this situation only air is present between primary and secondary coils.
Capacitor – energy storing component
The Tesla coil requires one more component, which is a capacitor. Here, the primary task of the capacitor is to store the charge and fire it all in one huge spark. The circuitry of the coil contains a capacitor and a small hole (known as a spark hole). When the circuit is turned ON, electricity flows through the circuit and fills the capacitor with electronic charges (electrons). These stored charges create their electric potential or voltage in the circuit, which tries to bridge across the spark gap between the primary (transmitter) coil and secondary (receiver) coil. This phenomenon can only happen when a large number of charges have built up inside the capacitor.
Once a much amount of charge has accumulated inside the capacitor then it breaks down the electrical neutrality of the air in the middle of the primary and secondary coil (also known as spark gap). The circuit closes for a fraction of seconds and a huge amount of charges blast out of the capacitor and through the coil. This produces a very strong magnetic field in the primary coil.
On the other side, the secondary coil uses electromagnetic induction to convert this magnetic field to an electric potential. That’s how Tesla coil works. Tesla might not have invented a source of unlimited energy, which was his goal while creating Tesla coil, but his design became the pioneer for many innovations for modern technology.
Normally Tesla model contains both coils in a similar structure to generate a powerful spark in the open atmosphere. The normal application of this model is to perform the arch attack.