How did J.J. Thomson’s research help explain thermionic emission?

In 1899, J.J. Thomson significantly advanced the understanding of thermionic emission by defining the nature of the negative charge carriers involved in the process.1

By analyzing the ratio of charge to mass of these particles, Thomson discovered that they corresponded to the same electrons he had identified in 1897 during his research on cathode rays. This established that the current observed in the Edison effect—where electricity passes from a heated filament to a metal plate—was caused by the actual emission of electrons from the hot material.123

Thomson’s work provided the fundamental insight that these particles were present in all matter, confirming that the phenomenon was not a unique property of specific gases but a universal characteristic of electron behavior in heated metals. This discovery laid the essential groundwork for the development of thermionic power converters and other vacuum tube technologies.213