CURRENT ELECTRICITY — Physics STD 12 Science — Question
Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsCURRENT ELECTRICITY2 Marks
Question
Explain the classification of material in terms of resistivity.
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Answer
→All materials fall under any one of these categories : (1) conductor (2) semi conductors and (3) insulator. →Among conductors, semi conductors and insulators, conductors have the lowest resistivity and insulators have the highest resistivity. →The resistivity of metals (conductors) is in the range of $10^{-8} \Omega m$ to $10^{-6} \Omega m$. →The resistivity of an insulator is $10^{18}$ times higher than the metals. →The resistivity of a semi conductor lies between the conductor and the insulator. →By increasing the temperature within a certain limit, the resistivity of metals increases with temperature while the resistivity of semi conductors decreases with temperature. →The resistivity of semi conductors is also affected by presence of small amount of impurities. →This feature is useful to make electronic devices from the semi conductors.
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