ELECTRONICS 1

Electronics is the field of engineering and applied physics dealing with the design and application of devices, usually electronic circuits, the operation of which depends on the flow of electrons for the generation, transmission, reception, and storage of information. 

 The information can consist of voice or music (audio signals) in a radio receiver, a picture on a television screen, or numbers and other data in a computer. 

BEHAVIOR OF DISCRETE ELECTRONIC COMPONENTS 

Electronic components are specially designed electronic elements which have leads with which they are connected to the circuit board.

 Electronic circuits consist of inter-connections of electronic components. Components are classified into two categories—active or passive. Passive components are components that never supply more energy than they absorb. 

Examples are resistors, capacitors and inductors. Active components are components that can supply more energy than they absorb. Examples are batteries, generators, vacuum tubes, and transistors. Resistors Resistors are made from carbon mixtures, metal films, or resistance wire and have two connecting wires attached. They are Specific Objectives After completing this chapter, you will be able to:  Observe the behaviour of discrete electronic components in a d.c. and a.c. electronic circuit. I

BEHAVIOR OF DISCRETE ELECTRONIC COMPONENTS used for current control in electronic circuit. Variable resistors, with an adjustable sliding contact arm, are often used to control volume on radios and television sets. Fig.

Some types of resistors Capacitors Capacitors consist of two metal plates that are separated by an insulating material. If a battery is connected to both plates, an electric charge will flow for a short time and accumulate on each plate. If the battery is disconnected, the capacitor retains the charge and the voltage associated with it. Rapidly changing voltages, such as caused by an audio or radio signal, produce larger current flows to and from the plates; the capacitor then functions as a conductor for the changing current. This effect can be used, for example, to separate an audio or radio signal from a direct current in order to connect the output of one amplifier stage to the input of the next amplifier stage. 

Some types of capacitors Inductors Inductors consist of a conducting wire wound into the form of a coil. When a current passes through the coil, a magnetic field is set up around it that tends to oppose rapid changes in current intensity. As a capacitor, an inductor can be used to distinguish between rapidly and slowly changing signals. When an inductor is used in conjunction with a capacitor, the voltage in the inductor reaches a maximal value for a specific frequency. This principle is used in a radio receiver, where a specific frequency is selected by a variable capacitor. 

 Inductors Transistors Transistors are made from semiconductors. These are materials, such as silicon or germanium that are doped (have minute amounts of foreign elements added) so that either an abundance or a lack of free electrons exists. In the former case, the semiconductor is called n-type, and in the latter case, p-type. By combining n-type and p-type materials, a diode can be produced. When this diode is connected to a battery so that the p-type material is positive and the n-type negative, electrons are repelled from the negative battery terminal and pass unimpeded to the p-region, which lacks electrons. With the battery reversed, the electrons arriving in the p-material can pass only with difficulty to the n-material, which is already filled with free electrons, and the current is almost zero.