* Electron Beam: The picture tube works by using an electron beam that scans across the screen, exciting phosphors to create the image. Electrons are negatively charged particles, and their flow constitutes an electric current.

* Vacuum: The tube is evacuated (a vacuum) to prevent the electron beam from colliding with air molecules and being scattered.

* Conductivity: The inner surface of the picture tube is coated with a conductive material (usually a thin layer of graphite) to help guide the electron beam and prevent it from building up static charge.

Therefore, the presence of the electron beam and the conductive coating on the inside of the tube makes the picture tube a conductor.