How are electrons produced in an X-ray tube? - Leaving Cert Physics - Question (i) - 2005

Electrons are produced in an X-ray tube through a process that occurs at the heated cathode or filament. The filament is typically made of a material such as tungsten, which has a high melting point and is well-suited for this application.

When electrical current passes through the filament, it heats up due to its resistance. This heating causes the electrons in the filament's atoms to gain sufficient energy to escape from the surface of the filament, a phenomenon known as thermionic emission.

Thus, in summary, electrons are produced by heating the filament in the cathode, leading to thermionic emission.