An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an ionized, electrically conductive channel through a normally-insulating medium, often air or other gases or gas mixtures. Michael Faraday described this phenomenon as "the beautiful flash of light attending the discharge of common electricity".
A spark on a spark plug
Lightning is a natural example of an electric spark.
Benjamin Franklin drawing an electric spark to his finger from a key suspended from a kite string.
Gas stove burner - the electric spark flame igniter is shown at the left.
In electronics, electrical breakdown or dielectric breakdown is a process that occurs when an electrically insulating material, subjected to a high enough voltage, suddenly becomes a conductor and current flows through it. All insulating materials undergo breakdown when the electric field caused by an applied voltage exceeds the material's dielectric strength. The voltage at which a given insulating object becomes conductive is called its breakdown voltage and, in addition to its dielectric strength, depends on its size and shape, and the location on the object at which the voltage is applied. Under sufficient voltage, electrical breakdown can occur within solids, liquids, or gases. However, the specific breakdown mechanisms are different for each kind of dielectric medium.
Electrical breakdown in an electric discharge showing the ribbon-like plasma filaments from a Tesla coil.
A Tesla coil, showing several forms of electrical breakdown. On the right side of the aluminum high voltage terminal (top right) is a purple corona discharge. At the end of the wire projecting from the terminal (top left) is a brush discharge. The fluorescent tube lying on the stand is lit by a glow discharge induced by the radio frequency electric field. At bottom the Tesla coil apparatus is lit by an intense white light from an electric arc in a
Dielectric breakdown within a solid insulator can permanently change its appearance and properties. As shown in this Lichtenberg figure
