Ans.
(i) The filament is a tungsten wire and it is heated by passing current through it.
(ii) The filament is heated to generate electrons by the process of thermionic emission.
(iii) The anode is kept at positive potential w.r.t. to cathode in order to accelerate
electrons.
(iv) In order to accelerate the electrons emitted from the cathode towards the screen, a large potential difference is provided between anode and cathode.
(v) Vacuum is created inside the cathode-ray tube so that electrons could easily reach to the screen. In the presence of air or any other gas, electrons may be scattered and absorbed before reaching the screen of CRO.