General Technology – Electricity
Electricity is the set of physical phenomena associated with the presence of electric charge. Although initially considered a phenomenon separate from magnetism, since the development of Maxwell’s equations, both are recognized as part of a single phenomenon: electromagnetism. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others. In addition, electricity is at the heart of many modern technologies.
The presence of an electric charge, which can be either positive or negative, produces an electric field. On the other hand, the movement of electric charges, which is known as electric current, produces a magnetic field.
When a charge is placed in a location with non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb’s law. Thus, if that charge were to move, the electric field would be doing work on the electric charge. Thus we can speak of electric potential at a certain point in space, which is equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is typically measured in volts.
In electrical engineering, electricity is used for:
electric power where electric current is used to energise equipment;
electronics which deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies.
Electrical phenomena have been studied since antiquity, though progress in theoretical understanding remained slow until the seventeenth and eighteenth centuries. Even then, practical applications for electricity were few, and it would not be until the late nineteenth century that engineers were able to put it to industrial and residential use. The rapid expansion in electrical technology at this time transformed industry and society. Electricity’s extraordinary versatility means it can be put to an almost limitless set of applications which include transport, heating, lighting, communications, and computation. Electrical power is now the backbone of modern industrial society.