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Electrical and electronic engineering: what's the difference?

Electrical and electronic engineering: what's the difference?Electrical and electronic engineering are not just two names for the same thing! Mechatronic engineer Michael Chandler explains the differences.

Electrical and electronic engineering may sound similar, but they are very different. Both involve moving electricity around a circuit to power useful products and machines, but that is where the similarity ends!

How do they work?

The main difference between electrical and electronic circuits is that electrical circuits have no decision making (processing) capability, whilst electronic circuits do. An electric circuit simply powers machines with electricity. However, an electronic circuit can interpret a signal or an instruction, and perform a task to suit the circumstance. For example, a microwave oven often bleeps when it has finished cooking, to inform the user that his or her meal is ready.

Most modern appliances use a combination of electronic and electrical circuitry. A washing machine has an electrical circuit comprising a plug socket, fuse, on/off switch, heater and motor, which rotates the drum. The desired wash cycle and temperature are inputted by the user via the control panel. These instructions are interpreted by electronic circuits, which have been designed and programmed to understand what the user would like based on what buttons have been pressed. When the electronic circuit has interpreted these commands, it sends signals to the electrical circuit to operate the heater and motor, to heat and rotate the drum, for the time required.

A difference of scale

Most electronic components are very small, and require small direct current (DC) voltages. A single micro-processor, which will fit on the end of your finger, may contain hundreds or thousands of tiny components, some of which are only a few atoms wide! Electrical components tend to be larger, and use alternating current (AC) voltages. Whilst most electronic components operate on 3-12 volts DC, electrical appliances require 230 volts AC. In factories and power stations, however, components may require up to 11,000 volts, and most electricity travels around the UK at 400,000 volts!

Some products, such as computers, have far more electronic components than electrical components. Large industrial sites such as factories or power stations, however, have far more electrical components.

How do they work together?

The link between electronic and electrical circuits is typically provided by relays or transistors. These are essentially switches but, rather than being pushed manually like a light switch, are operated by a small current from an electronic circuit. Therefore, a small circuit - often with many tiny components -can be used to operate much larger electrical equipment. This makes using household and industrial products safer, and means they are smaller and more energy efficient.

Relays are mechanical devices which, when a small current is applied from an electronic circuit, a metal contactor closes the electrical circuit, allowing a much larger current to pass. Relays were however large and unreliable, and tended to require a lot of current. After repeated use, the moving parts become worn and stop functioning correctly. Transistors, however, can be made much smaller and require tiny amounts of current, and have no moving parts. The transistor was invented in 1948, and is arguably the most important invention of the last 100 years.

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