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Electronics

Electronics is a word that is hard to define. It was probably first used in the 1930's to describe industrial applications of the radio vacuum tubes developed for use in radio. Then transistors were invented and the name was applied to them as well. Today, vacuum tubes and transistors are used more outside the radio field than in it and radio is now thought of as just one of the many branches of electronics.

Apart from a tube, or more usually today a transistor, the basic electronic circuit also includes components known as resistors and capacitors and occasionally inductors as well. A resistor offers resistance to an electric current: it is used to control the flow of current in electronic circuits.

Capacitors consist basically of two metal plates separated by an insulating layer. They possess the ability to store electricity for short or long periods and so are very useful in electronics. Inductors are coils of wire. They too can store electrical energy in the form of a magnetic field which surrounds the coil when a current flows through it.

One important class of electronic circuits, known as logic circuits, forms the building blocks from which computers are made. Made from transistors, resistors and capacitors they can, for example, be designed to give an output signal when there is a signal on both of the inputs: this type is called an AND gate. Alternatively, they can be designed to give an output signal when there is an input signal on only one of two input connections: this type is called an OR gate. Many other arrangements are possible.

By using them and similar circuits electronics engineers are able to design equipment that will switch on TV cameras on spacecraft as far away as the Moon; switch on instruments on spacecraft approaching the planet Venus; and control the ignition circuits of the family automobile. The introduction of cheap micro-electronic circuits in the late 1960's is greatly speeding up the spread of electronic control.