Any electrical apparatus, however complex, is composed, essentially, of one or more devices employing inductance, resistance, or capacity.
They are the building blocks of electrical engineering.
The use of inductances permitted the development of transformers, electromagnets, electric motors, generators and similar appliances.
The use of resistors made possible the development of electric lights, electricheaters, controls, and the like.
But modern electrical engineering would have been impossible without the use of condensers--millions of condensers, of many types and sizes--some of them not much larger than a match head, others as big as a room.
THE COMING OF THE MODERN CONDENSER
The condenser is an old invention but a recent development. The first electrical condenser, the Leyden jar, was invented in 1746 by Deen Van Kleist. It was referred to by Benjamin Franklin as an "accumulator" of electrical energy. Later, it was used extensively in medical and wireless telegraph equipment. The Leyden jar remained practically unchanged for more than 200 years, retainingessentially the same shape, design and construction.
Forty years ago, in 1910, we already had a sizable electrical industry-all of it based on electrical devices employing primarily only inductance and resistance. The only practical power condenser then available was the glass Leyden jar, or its equivalent, the glass plates.