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The flow of electrons in an electric currentThe flow of electrons in an electric current Electrons are tiny particles that are parts of atoms. An electric current is a flow of electrons. Electronics is the study of how electrons behave and how they can be controlled so that they can do useful jobs. Nearly all the machines we use in our everyday lives—computers, phones, TV remote controls, games consoles, calculators, radios, cars and so on—contain electronic circuits that make them work. Electronics are especially important in information technology and telecommunications.

A thermionic triode valve amplifies electric signals.A thermionic triode valve amplifies electric signals.

First electronic devices

The study of electronics began at the end of the 19th century, and had its first practical use in the early 20th century in the development of radio communications. The first electronic devices were called thermionic valves. These included the diode valve, which allowed current to flow through it one way but not the other, and the triode, in which a small current could be used to control a much larger current. The parts of thermionic valves, some of which glowed red hot, had to be enclosed in a glass tube with the air removed to create a vacuum.

Wafers of silicon on a conveyor beltWafers of silicon on a conveyor belt


In 1883, US inventor Thomas Edison observed the flow of electrons (not known at the time) from the heated element inside his new incandescent lamp to a cooler metal plate. It was a one-way flow: it did not work in reverse. This effect, called the Edison Effect, was put to use by John Fleming in his invention of the diode valve.

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