Capacitors and inductors, microprocessors, digital processing, computers

CAPACITORS AND INDUCTORS

Electronic components are divided into 2 categories: active components (can act as amplifiers-transistor) and passive components (not have this effect-resistors-capacitors-inductors). A capacitor, or condenser, stores an electric charge. It consists of two metal plates with an insulating material between them (dielectric). The ability of a capacitor to store electric energy is called its capacitance. The larger the plates and the thinner the dielectric, the higher the capacitance. The basic unit of capacitance is the Farad (F), but it is used also microfarads (μF) and picofarads (pF). Capacitors don't permit DC to flow through it, but permit AC to pass. Capacitors are used in integrated electronic circuits, radios, tv, etc. An inductor, or inductance coil or choke, is a coil of wire wound around a supporting core. When a current running through the coil increases or decreases, and the magnetic field around the coil also increases or decreases, generating a current in the coil which opposes the original current. Inductors don't permit AC to flow through it, but make easy the passage of DC, because it does not change. They are used to control the flow of electricity and to serve as filter; they are used in tuners, transformers and ignition systems. The basics unit of inductance is the henry (H), but it is used also millihenry (mH) and microhenry (μH).

MICROPROCESSORS

The microprocessors is a chip with a memory which can store lists of coded instructions, and it can do a variety of jobs. It's like a brain, and the instructions can then be stored or sent to other devices. Electronic circuits work with two basic types of signals: analogue and digital. Analogue signals vary continuously in voltage or current. A variable voltage causes changes in light, sound, temperature, pressure, etc.; and an analogue circuits measures these continuously varying quantities. Digital signals are represent by limited number of valued. Most processing is done by logic circuits which can operate much faster than analogue circuits. In digital processing, words, numbers, are digital into a code of binary numbers, called "binary" because it uses only two digits: 1 and 0. All information are represented by combinations consisting of only these two digits. Each 1 or 0 is called a bit, a contraction of "binary digit". A group of 8 bits forms a byte. The earliest microprocessors used 4 bits, but microprocessors advanced can work at 8, 16, 32 or 64 bits.

DIGITAL PROCESSING

In digital processing there are three basic elements: memory, logic circuits and control circuits. Memory circuits store bits permanently or temporarily. It contain thousands of capacitors, connect to the system by a metal conductor, with transistors or diodes acting as switches. There are two basic kinds of memory circuits: RAM and ROM. ROM contains instructions, or programs, for operating the system, it's used to store information for short periods. When the power is turned off, all the stored charges are erased. Logic circuits, in the CPU, manipulate data according to instructions. During the processing, bits are stored temporarily in areas called registers. Binary digits represent the ideas "true" or "false", instead of 1 or 0.the process is carried out through small groups of circuits called logic gates. Large combinations of these gates can solve complex mathematical or logical problems. The control circuits organize the movement of bits through the system. This is done by means of an oscillator, called the clock, which generates continuous pulses. The bits move through the circuit, following the rhythm of the clock.

COMPUTERS

They are classified into 3 groups: mainframes, personal computer, embedded computers. Mainframes are the largest and fastest computers, they can handle core information and solve more complex problems than any other type. They are used, for example, as storing information produced by statistics. The fastest mainframes, called supercomputers, are used mostly by scientists and engineers for major projects, such as design of aircraft. Personal computer are used by one person at a time. There are portable models called notebook computers, palmtop or handheld computers. This computers have only one microprocessors, others have additional co-processors to handle special kinds of works. Personal computers may be interconnected by telephone lines: it's a network, and the central computers is called server. Embedded computers are control units built into the devices they control and they are usually single microprocessors. They are used by commercial airlines and military planes that help to control the aircraft. They also maintain the orbits of satellites.