Part 3/7:
The internal operation can be visualized as an electron flow from the heater to the plate, moderated by the grid. The heater emits a stream of electrons in a vacuum, which, in the absence of any control, would flow directly to the plate. However, the presence of the grid allows for modulation:
When a small voltage is applied to the grid, it acts as a barrier, resisting electron flow.
Adjusting this voltage can either allow more electrons to pass or block them, thereby controlling the current reaching the plate.
This control mechanism allows vacuum tubes to amplify signals. Even a tiny variation in the grid voltage can lead to a significant change in the current flowing to the plate, making the tube an effective amplifier.