BASIC ELECTRONIC COMPONENTS

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This post is all about  the basic components of electronics..so stay tuned for some valuable information....
1.0.0 INTRODUCTION

An electronic circuit is composed of various type of components. 
Some of these components are termed as active components because they take part in the transformation of the energy while other components, which only dissipate or store energy, are called as passive elements. The vacuum tubes, rectifier, transistors are some of‑ the common active while the resistances, which dissipate the power and energy storing elements such as capacitance and inductance are known as passive elements. The transformers may be regarded as a matching device. The success of any electronic circuit depends not only on proper selection of the active elements but on the passive and matching elements too. The proper function, of an active device is decided by the proper values of these passive elements. Hence the selection of these elements such as resistances, inductance, capacitance, and transformers not only require the proper attention,but also decide the proper function of the active devices as well as the circuit as a whole.

1.1.0 ELECTRONIC COMPONENTS :

These can be classified into

1.1.1 Passive Components: Components like resistance, capacitance inductance, and fall in this class. 
1.1.2 Active Components: They can be further classified as Semiconductor Devices : Semiconductor diode, zener diode, and varactor diode etc.Uni‑junction transistor, Bipolar junction transistor (BJT), FET, silicon, Controlled rectifier etc.

Vacuum Tube Devices : Vacuum tube diode, triode, Tetrode, Pentode, Hexode,Heptode etc.

Gas Tube Devices : Gas diodes, Thyratons etc.

Photo Sensitivity Devices : Gas photodiodes, photomultiplier tubes, photodiodes,light emitting diode, photosensitive transistor etc.Though there are devices, which are specific to particular frequency range and applications like microwave devices etc.

1.1.3 PASSIVE DEVICES:

1.1.4 RESISTANCES:

Resistors can be made to control the flow of current, to work as Voltage dividers, to dissipate power and it can shape electrical waves when used in combination of other components.

Basic unit is ohms.

1.1.5 RESISTIVE ELEMENTS:

Metal alloys, carbon and graphite used with binders etc. are the, usual resistive materials. The alloys used as resistance wire usually have higher specific resistances than the base metals and have lower temperature coefficient of resistance. The three most common types of resistance wire used are nickel‑copper, nickel. Chromium‑aluminum and nickel‑chromium. Carbon and graphite are used as the basic resistance materials when they are mixed and heated with proper variety of resin binders. These types of resistances are generally known as composition carbon type’s resistors. The resistive element may be either in the form of a film or a solid slug, which consists of a number of conducting particles held together by resin.

In the film type the base materials may be glass, ceramic and plastics. Resistors can be 

(i) fixed resistors with two ends,

(ii) variable resistor or potentiometers.

Resistors are specified by the value of resistance, in ohms maximum power dissipation in watts, and precision in %.

Types: Resistors can be designed in many ways by usage, shape, physical construction tolerances, resistances are of the following three types i.e.

1.1.6 FIXED RESISTORS:

1.1.7 SEMIVARIABLE RESISTORS:

1.1.8 VARIABLE RESISTORS:

The fixed resistances are those whose values cannot be changed. In case of semi variable types of resistances their values can be changed with help of a screwdriver. Semi variable types resistances are known as preset. In case of the variable resistances their values can be changed from zero to maximum with the help of a movable arm .

1.1.9 RHEOSTATE :

A wire wound pot that can dissipate 5 and more watts is often referred to as a rheostat. The resistance wire is wound on an open ring of ceramic which is covered with vitreous enable, except for the track of the wiper arm. Rheostats are used to control motor speeds, x‑ray tube voltages, ovens and many other high power applications.

2.0.0 THERMISTORS:

A Thermistor is non‑linear resistance made of semiconductor material that is extremely sensitive to change in temperature. For a small change in body temperature of a Thermistor, there is an appreciable change in its resistance, where as most conductors have a positive temperature coefficient, the thermistor can exhibits a positive or negative temperature coefficient, (NTC). The thermistor is mostly negative temperature coefficient resistances.The resistances of thermistor

decreases rapidly for increased temperature. The thermistor are used in wide variety of applications. They can be used in measurement and control of temperatures, time delay, temperature compensation

and liquid level indicators. The thermistor is available in the form of a disk, bead, or bolted assembly packages.

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2.1.0 VARISTORS

These are voltage dependent resistances. They also fall under the category of non‑linear resistors. According to the Ohm's Law the current is directly proportional to the impressed voltage but in case of varistors the current is proportional to the nth power of the impressed voltage i.e.

                                                                  I α Vn

where I is the current in Amperes and V is the impressed voltage on the Varistors. 

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2.1.1 CAPACITOR 

A capacitor (originally known as a condenser) is a passive two-terminal electrical component used to store energy electrostatically in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors (plates) separated by a dielectric (i.e., insulator). The conductors can be thin films of metal, aluminum foil or disks, etc. The 'nonconducting' dielectric acts to increase the capacitor's charge capacity. A dielectric can be glass, ceramic, plastic film, air, paper, mica, etc. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, a capacitor does not dissipate energy. Instead, a capacitor stores energy in the form of an electrostatic field between its plates. 

 

An ideal capacitor is characterized by a single constant value for its capacitance. Capacitance is expressed as the ratio of the electric charge (Q) on each conductor to the potential difference (V) between them. The SI unit of capacitance is the farad (F), which is equal to one coulomb per volt (1 C/V). Typical capacitance values range from about 1 pF (10⁻¹² F) to about 1 mF (10⁻³ F)

2.1.2 INDUCTOR

An inductor, also called a coil or reactor, is a passive two-terminal electrical component which resists changes in electric current passing through it. It consists of a conductor such as a wire, usually wound into a coil. When a current flows through it, energy is stored temporarily in a magnetic field in the coil. When the current flowing through an inductor changes, the time-varying magnetic field induces a voltage in the conductor, according to Faraday’s law of electromagnetic induction, which opposes the change in current that created it.

An inductor is characterized by its inductance, the ratio of the voltage to the rate of change of current, which has units of henries (H). Inductors have values that typically range from 1 µH (10⁻⁶H) to 1 H. Many inductors have a magnetic core made of iron or ferrite inside the coil, which serves to increase the magnetic field and thus the inductance. Along with capacitors and resistors, inductors are one of the three passive linear circuit elements that make up electric circuits. Inductors are widely used in alternating current (AC) electronic equipment, particularly in radio equipment. They are used to block the flow of AC current while allowing DC to pass; inductors designed for this purpose are called chokes. They are also used in electronic filters to separate signals of different frequencies, and in combination with capacitors to make tuned circuits, used to tune radio and TV receivers.