Question

The amplification produced by a triode is due to the action of
A. Filament
B. Cathode
C. Grid
D. Plate

Answer 1

To find whether the amplification produced by triode is due to which component, we have to study the construction of triode and the detailed explanation about each part. The triode is made up of four parts viz, filament, cathode, grid and plate.

Complete answer:
A triode is an electronic amplification device having three active electrodes. A triode is an electronic amplifying vacuum tube consisting of three electrodes inside an evacuated glass envelope: a heated filament or cathode, a grid, and a plate (anode).

A triode has a hot cathode electrode heated by a filament, which releases electrons, and a flat metal plate electrode to which the electrons are attracted, with a control grid consisting of a flat screen of wires between them to control the current. These are sealed inside a glass container from which the air has been removed to a very high vacuum.

Since the filament burns out, the tube has a limited lifetime and is made as a replaceable unit; the electrodes are attached to terminal pins which plug into a socket. The control grid is an electrode used in amplifying thermionic valves (vacuum tubes) such as the triode, used to control the flow of electrons from the cathode to the anode (plate) electrode. The control grid usually consists of a cylindrical screen or helix of fine wire surrounding the cathode surrounded by the anode.

In a valve, the hot cathode emits negatively charged electrons, which are attracted to and captured by the anode, which is given a positive voltage by a power supply. The control grid between the cathode and anode functions as a gate to control the current of electrons reaching the anode.

A more negative voltage on the grid will repel the electrons back toward the cathode so lesser get through to the anode. A less negative, or positive, voltage on the grid will allow more electrons through, increasing the anode current. A given change in grid voltage causes a proportional change in plate current.Therefore, the amplification produced by a triode is due to the action of the control grid.

Hence, Option C is correct.

Note: Filament is the cathode used for heating the sample and emitting electrons from the sample. Plate is the anode which attracts the electrons which are emitted from the filament. But, the control grid is between Anode and cathode which controls the amount of electrons passing through it and hence contributes to amplifying action.