Question

How are substance classified on the basis of resistivity? Give one example of each class of resistances.

Answer 1

Concept Used: Resistivity

Step 1: Definition of resistivity:

Resistivity is the characteristic property of a material. It can be defined as a resistance of a conducting material per unit length with unit area. The unit of resistivity is ohm-meter.

$\mathrm{Resistivity}\mathrm{\rho }=\mathrm{Resistance}\mathrm{R}\times \frac{\mathrm{Area}\mathrm{of}\mathrm{cross}\mathrm{section}\mathrm{A}}{\mathrm{length}l}$

Step 2: Classification of substances based on resistivity:

Resistivity differs from substance to Substance. Based on resistivity substances are classified into three types. They are

1. Conductors
2. Insulators
3. Semiconductors

Step 3: Types with examples:

Conductors: Substances having low resistivity are called conductors since they are good conductors of electricity. The resistivity ranges from ${10}^{-8}\mathrm{\Omega }\mathrm{m}\mathrm{to}{10}^{-6}\mathrm{\Omega }\mathrm{m}$.

Examples of conductors are Silver, gold, copper, Iron, etc.

Insulators: Substances that have high resistivity, that does not allow the flow of current is called Insulators. The resistivity ranges from ${10}^{12}\mathrm{\Omega }\mathrm{m}\mathrm{to}{10}^{20}\mathrm{\Omega }\mathrm{m}$

Examples of insulators are rubber, glass, paper, ebonite, etc.

Semiconductors: Substances have moderate resistivity, it partially conducts i.e. will not carry current like a normal conductor. The resistivity ranges from ${10}^{-6}\mathrm{\Omega }\mathrm{m}\mathrm{to}{10}^4\mathrm{\Omega }\mathrm{m}$

Examples of semiconductors are Germanium and silicon.