Question

On increasing the temperature what will happen to specific resistance of a conductor and to a semiconductor??
Give reason as well!

Answer 1

Electrical resistivity of conductor increases with increase in temperature.

p = p° [ 1 + ɑ ( T - T° ) ]

n of electron doesn't change with temp . but an increase in temp . increase the amplitude of vibrations of lattice iona of the metal and thermal speed of the elwctrons which act as carriers of current . Due to collision of free electron with drifting ions while drifting towards the positive end of the conductor become more frequent , resulting in decrease in relaxation time . Hence electrical resistivity increases .

Semi conductor like carbon , germanium , silicon etc ., with increase in temperature , the number density n increases exponetially and time of relaxation decrease . but the increase in n compensates more than decrease in relaxation time . that is why the resistivity of semiconductors decrease exponentially with increase in temperature .