The spark gap is considered the very first electronic component made by man. It was invented much earlier than the vacuum tube, transistor and electric motor. And it is also easy to make it yourself at home.
Instructions
Step 1
The simplest spark gap is a ball spark gap. As its name suggests, it consists of two metal balls. The diameters of the balls have little effect on its breakdown voltage; it depends much more strongly on the distance between them, the composition of the gas mixture in which they are located, and the pressure of this gas mixture.
Step 2
It can be approximately assumed that in air at atmospheric pressure, the breakdown voltage of a ball spark gap in kilovolts is equal to the distance between balls in millimeters. By connecting a current-limiting resistor in series with the spark gap to prevent a short circuit and making a mechanism from a good insulating material to change the distance between the balls, such a primitive device can very accurately measure high voltages. If the voltage is variable, its peak value will be measured.
Step 3
A spark gap works much more efficiently, the electrodes of which have a shape that is different from a spherical one. The sharper they are, the lower the breakdown voltage will be under the same conditions (distance between electrodes, type of gas mixture, pressure). In a device with electrodes in the shape of needles, the breakdown voltage is much lower under the same conditions than in a spark gap that uses balls.
Step 4
An arrester has interesting properties, the electrodes of which are not the same. If one of them is a needle and the other is a plate perpendicular to it, its breakdown voltage strongly depends on the polarity. In a certain voltage range, such a device is even capable of rectifying, which is sometimes used in some laboratory installations until now.
Step 5
Due to its nonlinear properties, it can act as an active element of a relaxation generator. As you know, such a generator consists of a power supply with a large internal resistance, a capacitor, and any element with a negative dynamic resistance: a dinistor, a neon lamp or a spark gap.
Step 6
An ordinary school electrostatic machine contains all the elements that should be part of a relaxation generator. That is why, when its handle rotates, the discharges between the electrodes occur at a certain frequency, which depends on the rotational speed of the handle (it determines the charge rate of the Leyden jars) and the distance between the electrodes (which determines the breakdown voltage of the spark gap).
