Nikola Tesla


Nikola Tesla

Nikola Tesla (1856 – 1943) is the inventor of the modern alternating current system, radio, remote control, the first hydro-electric power plant at Niagra Falls, the Tesla Coil, and what he called his “best invention” in his autobiography: the wireless transmission of energy around the globe. These are only some of the highlights of the 700+ patents he held.

Despite these mind-boggling and visionary inventions, you usually do not read much about him in university text books, which has been one of the main motivations for starting this website.


Quenching is the art of extinguishing an arc in a spark gap. This results in better spark gap performance, because the sooner you extinguish an established arc, the sooner the capacitors can recharge for the next discharge.

To read about all the ways to quench a spark gap, click here.

Rate of change

The rate of change, in the case of electrical engineering, is the rate at which the voltage changes over a period of time, and is denoted in volts/second. The rate of change could therefore be called the slew rate.

rate\thinspace of\thinspace change = \frac{change\thinspace in\thinspace voltage}{T}

Where T is the period in seconds.

So if there is 40.000 volts discharging through a spark gap in 20ms, the rate of change is

rate\thinspace of\thinspace change = \frac{40.000}{0.02} = 2.000.000 volts/second

The rate of change can increase while the frequency remains steady, for example by increasing the amplitude or by reducing the duty cycle, in the case of condenser discharges.

Figure 1. Disruptive discharge vs function generator square wave

Series static gap

A type of spark gap in which the arc is spread out over multiple conductors, distributing the heat, hot ions and voltage.

Series static gap
Figure 1. Series static gap

To read more about this and other types of spark gaps, click here.

Spark gap

In its simplest form, a spark gap is nothing more than two electrodes with some space in between through which an electric spark passes when the voltage in a circuit reaches a high enough level.

Nikola Tesla developed this concept further and came up with several ingenious spark gap designs, using different types of materials, quenching and discharge mediums.

Tesla Coil

A Tesla Coil is a loosely coupled resonant transformer, which Tesla used to create high frequency, high voltage currents, and later to transmit energy through the earth. Modern day “Tesla Coilers” use this type of circuit to create big sparks, but Tesla himself on the other hand aimed to suppress spark losses from the top terminal by maximizing the surface area, as can be seen in the following patent drawing:

Tesla Magnifying Transmitter
Figure 1. The top terminal consists of several spherical surfaces to maximize surface area and minimize losses due to spark discharges

Tesla powered his Tesla Coils by discharging capacitors through a spark gap, which in turn set up a high-frequency oscillating current in a primary of a few turns. This also induced an oscillating current in a secondary of many turns, due to resonant inductive coupling, which greatly increased the voltage. Modern Tesla Coils are now often powered by a function generator + amplifier combination.

Vacuum tube

A type of spark gap in which two electrodes are enclosed in a vacuum.

Vacuum tube spark gap
Figure 1. Vacuum tube spark gap

To read more about this and other types of spark gaps, click here.