Final answer:
A vacuum tube is normally drawn alone because it is an electronic device that controls electric current with the help of a vacuum. Vacuum tubes were widely used in early electronic devices, such as radios and televisions, before the advent of transistors.
Step-by-step explanation:
In Physics, a commonly drawn alone is a vacuum tube.
A vacuum tube is an electronic device that controls electric current with the help of a vacuum. It consists of electrodes enclosed in a vacuum-sealed glass container. Vacuum tubes were widely used in early electronic devices, such as radios and televisions, before the advent of transistors.
Vacuum tubes are drawn alone because they are no longer commonly used in modern electronic devices. Transistors and integrated circuits have largely replaced vacuum tubes due to their smaller size, higher efficiency, and faster speed.