WHAT IS CONDUCTOR , INSULATOR , SEMICONDUCTOR ?

Free Electron 

Those electron which are free to move randomly at any temperature is called free electron . current electricity is possible only because of free electron . 
Electric force on free electron  ( Fe = - eE )    { since ,   force = qE }
 free electron  travel opposite of electric field . 

💢CONDUCTOR 

Those substance which consist of large number of free electron is called conductor . 

conduction of electricity and heat take place in easy way in the conductor .

Example -: metal , graphite , earth  etc 

free electron  travel opposite of electric field inside the conductor . 

 Inside conductor electric field is 0 every where in static condition

 because free electron will distribute themselves till the electric field is 0

 inside conductor . 

👉 Electric field is directed perpendicular to the surface of conductor . 

👉 conductor is an equipotential surface . 

👉In moving charge on conducting surface workdone is 0 .

Any excess charge must reside at the surface of conductor prove  from gauss law  ?     

Hence we can conclude that electric charge always reside at the surface of conductor .

💢 INSULATOR 

☆ The materials in which all the electrons are tightly bound to their respective atoms or molecules is called insulator. in simply way  we can say that there is no  any conduction of heat and electricity in insulator. 

☆ It does not contain any free electron.

☆when such type of material is placed in an electric field then the electron which is present inside slightly shift opposite to the field but they can't move through long distances .such type of material is also called dielectric.

example-:

 cotton , plastic , bottle , glass ,  hand gloves ,  etc 

RAILWAY INSULATOR 

💥SEMICONDUCTOR 

The material in which the number of free electrons is much smaller than in conductor , and its behaviour is in between a conductor and an insulator is called semiconductor .

The behaviour of semiconductor is like a insulator at the temperature of 0 K . only at high temperature some of free electron respond to the applied electric field . 

EXAMPLE -: 

germanium , silicon  gallium arsenide etc 

Also read this  post  Gauss's law

I hope this will helpful for you .

Thank you for reading my post .

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