Which side of the x-ray tube is negatively charged during exposure?

The cathode side of the x-ray tube is negatively charged during exposure. This is because the cathode is where thermionic emission occurs; it contains the filament that is heated to release electrons. These electrons are then accelerated toward the anode, which is positively charged. The separation of charges is crucial for the production of x-rays, as the movement of electrons from the negatively charged cathode to the positively charged anode creates the necessary interactions to generate x-rays when the electrons strike the anode target.

In the context of x-ray tube operation, the other options do not correctly describe the charged side of the x-ray tube during exposure. The anode is positively charged, neutral refers to an absence of charge which does not apply to the components involved, and ground is related to electrical safety and does not define the charge of the x-ray tube components during the imaging process.