Electrons are tiny particles that whizz around the centre (nucleus) of an atom. An electric current is a flow of electrons. This flow of electrons can be controlled so that it can do useful jobs. The way this is done is called electronics. Nearly all the machines we use in our everyday lives—computers, phones, TV remote controls, games consoles, calculators, radios, cars and so on—use electronics to make them work.

Electronic circuits

Electronics uses electrical circuits. A circuit is produced when a flow of electrons—an electric current—moves along a complete path of conducting material—say, a wire—from a power source, such as a battery, and back again. An electronic circuit links together electronic components (for example, resistors, capacitors, light-emitting diodes and transistors) in an electrical circuit.
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By using different components and connecting them in different ways, it is possible to make electronic circuits carry out almost any job. Electronics are used, for example, in a security light on the outside of a house. The electric current is turned on or off by electronic components. These detect whether it is dark or not, and whether anybody is moving nearby.

Digital electronics

In many electronic circuits, such as those in old radios, the electric current can be of any strength. These circuits are called analogue circuits. In digital circuits, the current can have only two strengths: on or off. Digital circuits are used in computers and smartphones. In these devices, the on/off patterns of the flow of electricity are controlled to represent information or data.

Bytes

Any number can be represented by a "word", or code, made up of just two "bits": 1 and 0. The four-bit code 1101, for example, represents the number 13 (one 8, one 4, zero 2s and one 1). An eight-bit code, which can represent a much bigger number, is called a byte.

​​​​​​​Data—text, images, sounds and videos—can be turned into a series of bytes. They can be represented in a digital circuit by controlling the flow of electricity—0 is for “off” and 1 is for “on”—through the circuit. Computers store this data on an enormous series of microscopic transistors, each of which is either on or off.

Pixels

Anything that appears on a computer monitor or smartphone screen is called computer graphics. These are made up of tiny coloured dots called pixels (short for picture elements) in a grid pattern. The concentration of pixels in a picture is called resolution.

High-resolution (hi-res) graphics—made up of high numbers of pixels per square centimetre—are viewed on a screen without the pixels being visible to the naked eye. The very small portion of this image of Tower Bridge, in London, shown here, is made up of 100 pixels.

Each pixel on a screen has its own particular position, colour and brightness. This information is represented by a code that is unique to each pixel. The entire image, made up of millions of pixels, is stored on the computer as millions of bytes.

Microchips

Digital circuits that require thousands, or even millions, of electronic components would be enormous if they were made by wiring the components together. This is why digital electronic circuits in computers and smartphones use integrated circuits, or microchips.

A computer is made up of hardware—all its parts—and software, which is made up of the information stored and the programmes it uses. Personal computers include laptops, tablets and smartphones.

Computer networks

A computer network allows computers to exchange information between each other. The connections, or are made either via cables (usually fibre optics) or wireless (radio waves). The internet is an enormous worldwide computer network.

​​​​​​​Instead of storing information and programmes on your computer, you can use the internet to store them. Some websites act as special information centres. This is called cloud storage. Social networking sites, such as Facebook or Tiktok, are examples of cloud storage.