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An electronics engineer comes in contact with a large variety material in the manufacturing of a apparatus,electronic machines & electronics devices,radio,TV,electronic gear,automatic & remote control euqipment.In transmission line design,we must have knowledge material.In computor memory device too,
We must have an undrestanding of the construction of IC’s & Semi Conducting materials.The materials used in various branches of electronics engineering
they are divided into two large groups.
The first group comprises of construction materials which mainly go into the manufacture of bearing and auxiliary parts and components of electrical and
radio devices,such as mounting rames,cases,dials,heat sinks,etc…The second groups includes materials use for the fabrication Wires,Cabels,Wave Guides,
Antennas,Insulators,Capacitors,Resistors,Inductors,Transformers,Electric Motors & Generators,Magents,Diodes & Transistor,FET& integrated Cicruits (IC),
Electromechanical Transducers,Lasers,Light Detectors,Computor memary devices & so on.
According to electrical properties,the materials can be classified into the following groups.
01)Conductor materials
02)Semiconductor materials
03)Super Conductor materials
04)Magnetic materials
05)Ferromagnetic materials
06)Insulating materials (Dielectrics)
07)Ferrimagnetic materials
08)Ferroelectric materials
09)Gaseous Insulator
10)Gaseous Conductors
In this fast developing society,electronics is the most important branch of engineering.Eletronics devices are being used in almost all the industries for the quality controls and automations.the branch of electronics which deals with current conduction through a vaccume or gas or semiconductor.
Now we will see about semiconductor.
Certain substances like Germanium,Silicon,Carbon etc.. are neither good conductor like copper nor insulators like glass,wool,rubber etc. thats why we can say,semiconductors are those substances whose eletrical conductivity lies between conductors and insulators,for example Germanium,Silicon,selenium,
carbon.The resistivity of semiconductor materials lies between 0.01 to 50 ohm centimeter at room temperature.The resistivity of semiconductor is not constant,but varies with many factors.The resistivity can be controlled by an electric field,voltage,temperature,illumination and impurity.Such resistivity controlled
materials then works as transistors,varistors,photoelectrics and rectifiers.
Properties of Semiconductors.
01)The resistivity of semiconductor is less than an insulator but more than a conductor.
02)Semiconductors have negative tempratures coefficient of a resistance. i.e.The resistance of semiconductors decreases with the increasing tempratures and vice versa. for example Germanium actually an insulotor at low temprature but it becomes a good conductor at high temprature.
03)When a suitable metallic impurity ( Arsenic,Gallium etc.) is added to a semiconductors,it’s current conducting properties changes appreciably.This is the most important property.
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