Question

if electricity doesn't conduct through vacuum then how does a vacuum tube works​

Answer 1

Answer:

Good question! The answer is that the vacuum is an insulator simply because it does not contain any charges that can move to carry current. A vacuum tube really doesn't contain a vacuum. It contains a cloud of electrons that spew out from a hot wire - like the filament of a light bulb. Turn off the current that heats that wire, and no current will flow in an old-style vacuum tube.

If someone made a vacuum tube using light and the photoelectric effect to generate a cloud of electrons, current could only flow as long as the light is shining on the photocathode