CBSE NOTES CLASS 12 PHYSICS
CHAPTER 14 SEMICONDUCTORS
TYPES OF SUBSTANCES ON THE BASIS OF CONDUCTIVITY
Metals on the basis of conductivity
Conductors are those substances through which electricity can pass easily, e.g., all metals are conductors. They possess very low resistivity (or high conductivity).
ρ ~ 10–2 – 10–8 Ωm
σ ~ 102 – 108 Sm–1
Semiconductors on the basis of conductivity
Semiconductors are those substances whose conductivity lies between conductors and insulators, e.g., germanium, silicon, carbon etc. They have resistivity or conductivity intermediate to metals and insulators.
ρ ~ 10–5 – 106 Ωm
σ ~ 105 – 10–6 Sm–1
Insulators on the basis of conductivity
Insulators are those substances through which electricity cannot pass, e.g., wood, rubber, mica etc. They have high resistivity (or low conductivity).
ρ ~ 1011 – 1019 Ω m
σ ~ 10–11 – 10–19 S m–1