Majority Charge Carrier & Minority Charge Carrier

  • There are no free charge carriers at 0 oK in the pure Silicon / Germanium.
  •  However, when the room temperature increases, some of the covalent bonds are broken by heat energy. 
  • This will result in electron – hole pairs are produced; it is called as thermally generated charge carriers

Mobile Charge Carriers & Immobile Ions


P type semiconductor

  • The P type semiconductor material is formed by addition of acceptor type impurity atoms ( gallium, indium, aluminum, boron ) to pure silicon / germanium crystals. 
  • The number of holes added is equal to the number of boron atoms ( acceptor impurities ) because each atoms contribute one hole. 




The conductivity arises form mobile charge carriers of the semiconductor. 

Types of matter

Mobile charge carriers



Ionized gas

Electrons & positive charged ions


Position ions and negative ions



Bohr's Atomic Model


The atomic model is proposed by Bohr in 1913. The Bohr has made following assumptions.

  • The atom has massive positive charged nucleus.
  • The electrons revolve round their nucleus in circular orbits. The centrifugal force between electron and nucleus is balanced by electrostatic pull.


Harmonic Resonance


  • Sometimes harmonic resonance occurs between power capacitor and transformer which may cause high magnification of harmonics. 
  • The resonance can happen at one particular frequency is called as resonance frequency ( fr )  in a system in which inductive reactance       ( XL ) and capacitive reactance ( XC ). 
  • The net impedance becomes low when the inductive reactance XL is equal to capacitive reactance XC


Atoms, Molecules & Ions



  • The smallest particle of any object is called as atoms. 
  • Every object is made of atoms. 
  • However, the entire world is made of matters. 
  • The atoms are very small and they measured in the nanometers.



  • According to Bohr , an atom is composed by number of electrons moves in circular or elliptical orbits around the center nucleus. 
  • The nucleus consists of protons and neutrons.
  • Mass of electron = 9.1 × 10 – 31 kg
  • Charge of electron = 1.6 × 10 – 19 coulomb