Electron Tubes

Multiple-choice exercise

Read the text and choose the correct noun for each numbered space.

Electron Tubes

Electron [1] consist basically of a metal, ceramic, or glass [2], evacuated of air to some degree or filled with a gas such as mercury vapour, and incorporating two or more [3]. One of the [4], the cathode, must be heated in order to provide the [5] of [6] needed for the electron tube to function. These [7] are used in electronic circuitry, radio and television, and radar [8]; and they have a large number of research and industrial [9]. For some [10] electron [11] have been replaced by solid-state [12] such as the [13], which take up less space, use lower voltages, and do not need a heated [14]. For uses requiring high power, however, electron [15] remain essential.