Fill in the blanks:
$(i)$ When amber or ebonite is rubbed with silk or fur,it produces $......$.
$(ii)$ In a discharge tube,the stream of particles flows from cathode to anode. This is called $......$.
$(iii)$ In a cathode ray tube,a coating of $......$ is applied as a fluorescent material.
$(iv)$ $A$ television picture tube is a type of $......$ tube.