Metallic bond

Ionic bond

Covalent bond

van der Walls bond

the valence electrons of atoms move freely like gas molecules in a solid

the valence electrons of atoms move under coulomb field of atoms but they themselves do not apply any force on each other and like gas molecules in a solid

the valence electrons of atoms move under coulomb field of atoms

all electrons move freely in side solid

$$\frac{ne\tau}{m}$$  

$$\frac{ne2\tau}{m}$$  

$$\frac{\eta e}{m}$$  

$$\frac{m}{ne2\tau}$$  

Ohm's law and Widemann Franz law

Ohm's law and conduction in semiconductor

Ohm's law and Jule's law

Ohm's law anFaraday's law

$$K\ =L\sigma T$$

$$\frac{K}{T}=L$$

$$\frac{K}{T}=\sigma$$

$$K\sigma=T$$

Drude used particle picture and Somerfeld used wave picture

Drude used wave picture and Somerfeld used particle picture

Drude used only electronic case and Somerfeld considered both electron and hole

Drude used both for electron and hole and Somerfeld used only for electron

$$\frac{3}{2}KT$$

$$\frac{n2\pi2h2}{2\pi m2}$$

$$\frac{n\pi h}{2ma2}$$

$$\frac{n2\pi2h}{2\pi m2}$$

this picture represents electrons in infinite periodic potential

this picture represents electrons in a finite potential well

this picture represents electrons in a finite periodic potential well

this picture represents electrons in a infinite potential well

electrons are moving freely without any interaction btn. themselves or atomic nuclei

electrons are moving freely without any interaction btn. themselves but under Coulomb field of atomic nuclei

electrons are moving freely between Coulomb interaction btn. themselves but under Coulomb field of atomic nuclei

electrons are moving freely between mechanical interaction btn. themselves but under Coulomb field of atomic nuclei