Electronics is the study and use of
electrical devices that operate by controlling the flow of electrons or other
electrically charged particles. These devices include vacuum tubes and semiconductors.
Some people study how such devices work in general, as part of physics.
Other people design and construct electronic circuits to solve practical problems. This is part of
electrical, electronic and computer engineering.
Most
electronics systems fall into one of these two categories:
Some electronic circuits process and distribute information. These are communication systems.
Other electronic circuits convert and distribute energy. These are control systems.
One way of looking at an electronic system is to divide it into the following parts:
Inputs - Electrical or mechanical sensors (or transducers), which take signals (in the form of temperature, pressure, etc.) from the physical world and convert them into current/voltage signals.
Signal processing circuits - These consist of electronic components connected together to manipulate, interpret and transform the signals.
Outputs - Actuators or other devices (also transducers) that transform current/voltage signals back into useful physical form.
Take as an example a television. Its input is a broadcast signal received by an antenna or fed in through a cable. Signal processing circuits inside the television extract the brightness, colour and sound information from this signal. The output devices are a cathode ray tube that converts electronic signals into a visible image on a screen, and magnet driven audio speakers.