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The mysterious power of electric sparks: Why can it ignite everything in an instant?
A spark is a sudden electrical discharge that occurs when a sufficiently strong electric field creates a charged conductive path in a normally insulating medium such as air or other gases. spark. This phenomenon led many scientists, such as Michael Faraday, to praise it as "a beautiful flash of light accompanying the ordinary discharge of electric current."
The rapid transition of the spark from a non-conductive state to a conductive state is accompanied by a brief flash of light and a crisp popping sound.
Sparks occur when the applied electric field exceeds the dielectric breakdown strength of the medium. For air, its breakdown strength is about 30 kV/cm at sea level. Different experiments will show variations in this number, depending on humidity, atmospheric pressure, the shape of the electrodes (e.g. needle-shaped and flat, hemispherical, etc.) and the distance between them, and even the type of waveform, such as a sine wave or Cosine rectangular wave.
In the initial stage of current flow, free electrons in the gap (from cosmic rays or background radiation) are accelerated by the electric field, causing a Townsend avalanche. When these electrons collide with air molecules, they create more ions and newly generated electrons, which are also accelerated. Eventually, the thermal energy provides a large source of ions, causing dielectric breakdown in the region within the void.
Once the void breaks down, the limit to current flow is determined by the available charge (e.g., electrostatic discharge) or the impedance of the external power source. If the power source continues to supply current, the spark will turn into a continuous discharge phenomenon called an arc. Electric sparks can also occur in insulating liquids or solids, but their breakdown mechanism is different from that of sparks in gases.
History of EDM
In 1671, Leibniz discovered that sparks were related to electricity. In 1708, Samuel Wall conducted an experiment to produce sparks by rubbing rubber against cloth. In 1752, Thomas François Dallibard arranged for a French veteran to collect lightning in a Leyden jar in the village of Marly, based on an experiment proposed by Benjamin Franklin, proving that lightning and electricity are the same phenomenon. And Franklin's famous kite experiment was an example of successfully extracting sparks from clouds during a thunderstorm.
Applications of EDM
Ignition Source
An electric spark is used in the spark plug of a gasoline internal combustion engine to ignite the fuel and air mixture. The charge in the spark plug is discharged from the insulated center electrode to the ground terminal. The voltage for the spark is provided by an ignition coil or magneto generator and is connected to the spark plug via insulated wires. Flame igniters use an electric spark to start combustion on certain stoves and gas burners, replacing the traditional flying flame.
Wireless Communication
Spark gap transmitters use an electrical spark gap to generate radio frequency electromagnetic radiation that can be used as a transmitter for wireless communications. Spark gap transmitters were in widespread use for the first thirty years, from 1887 to 1916, but were then superseded by vacuum tube systems and were no longer used for communications before 1940. The widespread use of spark gap transmitters led to "Spark" becoming a nickname for ship radio operators.
Metalworking
Electrical sparking is also used in a variety of metalworking techniques. Electrical discharge machining (EDM), sometimes called spark machining, uses spark discharges to remove material from a workpiece. This technology is mainly used for hard metals that are difficult to process using traditional techniques. Spark plasma sintering (SPS) is a sintering technique that involves passing a pulsed DC current through a conductive powder in a graphite die. SPS is faster than traditional hot isostatic pressing.
Chemical Analysis
The light produced by an electric spark can be used in a spectroscopic technique called spark emission spectroscopy. High-energy pulsed lasers can also be used to produce electrical sparks. Laser-induced breakdown spectroscopy (LIBS) is an atomic emission spectroscopy technique that uses high-energy pulsed lasers to excite atoms in a sample. This technique is also known as laser spark spectroscopy (LSS). Electric sparks are also used to create ions in mass spectrometry.
Dangers of electric sparksElectric sparks are dangerous to people, animals and even static objects. Electrical sparks can ignite combustible materials, liquids, gases and vapors. Even accidental static discharges, such as those generated when turning on lights or other circuits, can ignite sparks from flammable vapors such as gasoline, acetone, propane or powders in a flour mill.
If a person carries high-voltage static electricity or is near a high-voltage power source, sparks will jump between the conductor and his body, releasing huge energy, which may cause severe burns, damage to the heart and internal organs, and even cause Arc flash generation. Even relatively low-energy sparks, such as those from a stun gun, can overload the nervous system's electrical pathways, causing involuntary muscle contractions or disrupting the heart's rhythm.Sparks often indicate the presence of a high voltage field; the higher the voltage, the greater the distance the spark can travel.
Therefore, the electric spark is not only a fascinating physical phenomenon, it also triggers our deep thinking about safety, technology and application. Behind these phenomena, are there more unsolved mysteries waiting for us to explore?
