The Tesla coil is a special type of transformer used for producing high-frequency, high-voltage currents. The voltages may go as high as 1 MV. In other words, the Tesla coil is essentially a device for producing artificial bolts of lightning.
Handling the high-frequency Tesla coil, you will feel no electric currents since they only pass through the upper layer of the skin.
Experiments involving the Tesla coil are exciting to watch because we humans can feel the effects primarily through visual and hearing senses while not feeling the electricity itself at all. These experiments are particularly interesting in terms of popularizing physics since their effects can be interpreted on various scientific levels.
The Tesla coil consists of three functionally interconnected units: a supply transformer, spark gap with an oscillating electric LC circuit, and a capacitive terminal high-voltage transformer.
With his research at the turn of the 20th century and development of the Tesla coil, Nikola Tesla ushered in a new age in the wireless transmission of energy. This device provided the starting point for further exploration of high-frequency voltages, which led to the development of present-day radio, telephone and navigation technologies. These accomplishments are going to continue to drive the development of human society for quite some time in the future.