Immobility Phenomena and Reverse Driving Phenomena of the Electric Arc

When an electric arc is driven by a magnetic field, under special conditions, curious phenomena are observed. An electric arc cannot be driven by the magnetic field when it is established at very small gaps between the electrodes. Neither can it be driven by the magnetic field for the instant just after the contacts have been broken. These phenomena are called immobility phenomena. In the present work, the immobility time and the driving velocity of the electric arc were measured under various air pressures. As the air pressure decreases, the immobility time increases and the driving velocity decreases. Under a certain low air pressure, the arc cannot be driven by the magnetic field. When the air pressure is lower than this critical value, the arc can be driven again by the magnetic field; but in this case, the arc moves in a direction that is opposite to the direction of the electromagnetic force. This phenomenon is called the reverse driving phenomenon. The causes for these phenomena are considered.