What Is a Spark Spread?

In the case of ordinary air pressure and power supply, if a high voltage is applied between two cold electrodes with small curvature, the gas between the electrodes will be penetrated by a strong electric field to generate self-excited conduction. The phenomenon is spark discharge. The impact ionization produced by this discharge process is performed along a narrow and tortuous light-emitting channel, accompanied by sparks and violent sounds. ^[1]

Flashing and sounding transient gas discharge occurs between positive and negative charged areas with high potential difference. In the discharge space, gas molecules are ionized, and the gas quickly and violently generates heat, emitting flashes and sounds. The path traversed by the discharge channel and its luminous and conductive properties depend on the shape and size of the positive and negative charged areas, the potential difference between them, and the nature and pressure of the gas. Because the voltage between the two poles is very high at the time of spark discharge, but the power of the power is not large, once the discharge occurs, the current intensity increases sharply, but the voltage drops instead, causing the discharge to extinguish temporarily. The discharge will not be performed until the voltage is restored. Therefore, spark discharge is intermittent. Lightning is a large-scale spark discharge phenomenon in nature. In high-voltage devices, electric sparks may occur between parts with poor contact. This phenomenon consumes energy, damages the device and is easily dangerous.

Since the breakdown voltage that causes spark discharge depends on the shape of the electrodes and the distance between them when other conditions are unchanged, in high-voltage engineering, it is often measured by the distance when a spark discharge occurs between electrodes of a certain shape (called the spark gap). Unknown high voltage value. The following table shows the relationship between spark gap (mm) and voltage for several shapes of electrodes.

Voltage / V	Two dot electrode	5mm diameter Two spherical electrodes	Two flat electrodes
20000 40000 100000 200000 300000	15.5 45.5 200 410 600	5.8 13 45 262 530	6.1 13.7 36.5 75.3 114

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Main applications: Spectral analysis. Ignition of internal combustion engine. Metal electrical discharge machining: Use spark discharge to corrode metal workpieces in electrolyte solution to form the surface corresponding to the shape of the tool electrode (this machining method can perforate, sculpt and make various profiles on very hard metal Cavity). High voltage value measurement: Because the minimum voltage that causes spark discharge (ie, breakdown voltage, see "Gas discharge") is related to the shape of the electrode and the distance between the electrodes, it often occurs by measuring between electrodes of a certain shape in high voltage engineering The spark discharge interval is used to measure unknown high voltage values.

The starter of the fluorescent lamp also uses the principle of spark discharge. When the electric key of the fluorescent lamp is closed, the voltage causes the neon gas in the glass tube of the starter to discharge, and the heat generated by the discharge causes the moving piece in the glass tube to expand due to heat and connect the static piece. Flashes and clicks occur during the process. When the moving piece is disconnected from the static piece, the high voltage causes the mercury vapor in the lamp to discharge, and the fluorescent lamp emits light. ^[2]