⇒ They posses free electrons and their electrical resistance is quite less.
⇒ Non-metals are almost bad conductor of electricity as they don't possess any free electrons.(except graphite)
⇒ The elements in the fourth group of the periodic table like the Si and Ge have greater electrical resistance than the good conductors but have a lower resistance than the bad conductors.
⇒ Such elements are known as Semiconductors.
⇒ The mechanism of electrical conductivity is different in case of the good conductors and the bad conductors.
⇒ Semi-conductors behaves as bad conductors at zero kelvin temperature in their pure form.
⇒ The resistivity depends on temperature as in good conductors resistivity increase with temperature while in semi conductors resistivity descreases on increasing the temperature upto a certain limit.
⇒ Conductivity of semi conductors is also changed by making radiation incident of suitable frequency.
⇒ The electrical properties of any substance depends on the arrangement of the crystals and their composition of electrons.
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