ABSTRACT
Consider a circuit in which a battery is connected to a light bulb through a switch.
In this simple electrical system, chemical energy is converted into electrical energy in the battery. The electrical energy travels along the wires to the light bulb where it is converted into heat and light. The switch is used to interrupt the flow of electrical energy to the light bulb. Although such an electrical system may seem commonplace to us now, it was only invented about 100 years ago. For thousands of years before this, light and heat were obtained by burning oil or some other combustible fuel (e.g. wood). Although the concept of electric charge was known to the ancient Greeks, and electricity as we know it was well-studied in the 19th century, it remained a scientific curiosity for many years until it was put to use in an engineering sense. In the early part of the 20th century, electrical engineering was concerned with motors, generators and generally large scale electrical machines. In the second half of the 20th century, advances in the understanding of the electronic structure of matter lead to the emergence of the new field of electronics. Initially, electronic circuits were built around relatively large scale devices such as thermionic valves. Later, the functionality of valves was implemented using solid-state components through the use of semiconductors.
