Final answer:
Tube current is the current produced by an X-ray tube during exposure; it accelerates electrons towards the anode to generate bremsstrahlung and characteristic X-rays.
Step-by-step explanation:
The current produced by an X-ray tube during exposure is called tube current. This current is responsible for the ejection of electrons from the filament in the cathode and their acceleration towards the anode. When these electrons strike the anode material, such as copper, they decelerate and produce X-rays through two main processes: bremsstrahlung or braking radiation, and the emission of characteristic X-rays that are specific to the anode material. The electrons convert their kinetic energy into different forms including thermal energy and X-ray photons, which are part of the electromagnetic (EM) spectrum. X-ray tubes operate in a similar fashion to the cathode ray tubes (CRTs) found in older television and computer screens.