Explain : .Electrical resistivity is a characteristic property of the material..

Explanation

Metals and alloys have very low resistivity in the range of `10^(-8)Omegam" to "10^(-1)Omega m`.
A good conductor of electricity has low resistivity and a poor conductor of electricity has a high resistivity.
Insulators like rubber and glass have resistivity of the order of `10^12 Omegam " to " 10^(17) Omegam`.
Copper and aluminium have very low resistivity (of the order of `10^(-8)Omega m`) due to which they are very good conductors of electricity.
[And hence they are generally used for electrical transmission lines.]
Resistivity of alloys (e.g.. Nichrome, constantan) is higher (of the order of `10^(-6)Omegam`) than those of pure metals from which they are made.
[For this reason, they are commonly used in electrical heating devices like electric iron, toasters, etc.]
The resistivity of semiconductors like silicon (SI) and germanium (Ge) is between those of conductors and insulators and decreases on increasing the temperature.
[And hence they are used for making (PN junction) diodes and transistors.]