I found another interesting subject from americanradiohistory.com, a simple explanation about vacuum tubes.
From page 940 of the April-May 1922 edition of “Radio News” – one of many Gernsback publications – is this illustrated analogy:
Here, we see a pump on the right sucking water from a riser column inside a closed sphere. The pump is the stand-in for the battery in the electric circuit. The “grid” is a series of shutters that allow one to control the flow of water from the riser column to the collection “plate” which the pump is sucking on.
In a radio, the grid is controlled by the antenna. The small signals of the radio waves move the “shutters” slightly, but doing so causes a very large change in the flow of electrons between the filament (riser column) and plate. These changes can be heard or seen when presented via speaker or spark gap.
I thank americanradiohistory.com for digitizing these old publications and sharing them.