Tesla coil; working principles and applications

The Tesla coil is a giant coil of wire wound around a plastic or insulting pipe.

It is just like a transformer which inputs a low voltage high frequency alternating current and then step it into thousands or milions of volts, depending on how it is designed.

Essentially, a Tesla coil consists of a secondary and primary coil. 

The coil of wire which the current is applied to is called  the primary coil, while the secondary coil is the one which is linked to the primary coil by varying magnetic field.

The primary coil is usually made of few number of turns while the secondary coil is made up of large number of turns usually from hundreds to thousands of turns.

The  Tesla coil is a reasonant based electric  to which  steps up voltage applied to it primary coil into thousands to milions of volts. While steping up the voltage, at the same time a vast energy of electromagnetic field is generated which spreads out of the secondary coil. The Tesla coil when in operation produces sparks and lightning if the input voltage is large. Tesla coils can iluminate flourscent bulbs wirelessly, light up LEDs brought in contact with them.

History of the Tesla coil.

In the 1800s, electricity had long been discovered by Benjamin Franklin then, and it was no longer novel. 

In the 18th century, the technology and engineering of how to transmit, generate and utilize electricity was evolving, during this time, a genius electrical engineer and scientist "Nikola Tesla" (1856-1943) was on the cutting edge of research of how to transmit energy wirelessly over long distance without the use of wires.

In 1891, he invented what we call a Tesla coil(named after him as an honour). The Tesla coil was one of his greatest invention. 

It's simply a high-frequency transformer capable of creating very high voltage at low current. He built several variations of this coil. The most popular of his designs is made up of a transformer, capacitor, spark gap, main coil, minor coil and discharge sphere. 

Working principle of a Tesla coil.

The transformer inputs an alternating current of about 100 volts from an external power supply and steps  it up to as much as 25k volts or more by means of a neon transformer.

The capacitor stores the voltage until it reaches its limit, at which point the spark gap emits all of the pent-up energy in one massive outburst, surging to the main coil, which is often built out of wide copper wire, generating a powerful magnetic field. The current continues to the minor coil that serves as a transformer, utilizing the effects of the magnetic field to build enormous quantities of voltage. At this point, the electricity flows to a discharge sphere that emits the current as a stream or arc of sparks. 

Circuitry using the Tesla coil was part of the first generation of transmitters to carry wireless telegraphy. 

Basic parts of the Tesla coil.

1. Oscilator: for Tesla coils with DC as it input, an oscilator is needed to convert the DC voltage into an high frequency alternating current needed for producing varying magnetic field at the primary coil. Tesla coils can't work with DC, so an oscilator is needed to convert it into Alternating current for it to operate. If an AC is used to power the Tesla coil a capacitor and a spark gap is connected to the primary coil as shown in the schematic diagram above.
2. Secondary coil: The primary coil is made up of large number of turns wound very close to each other on a plastic pipe without overlapping. It is the basic parts of a Tesla coil responsible for producing giant sparks and lightning. One end of the coil is connected to the input power supply of the primary coil.
3. Step up transformer: A powerful transformer is use to step up input AC voltage from power supply into thousands of volts, which is then connected to the primary coil.
4. Metal sphere: A metallic sphere is usually placed above the Tesla coil and connected to one end of the secondary coil. It works as an amplifier for producing power electromagnetic field.