Question

A piece of copper and the other of geramnium are cooled from the room temperature to 80K . What will happen to their resistance ?

Answer 1

The resistance of copper( i.e conductor)  decreases and germanium (i.e semi-conductor) resistance increases.

Explanation:

As in the case of Number of electrons or holes -

$n_{e} = n_{λ } = AT^{\frac{3}{2} } e^{\frac{-E_{g} }{2KT} }$

Where ,

Eg = Energy gap

K = Boltzmann Constant

T = Temperature in kelvin

On increasing temperature,  the number of current carried increases

 As temperature is decreased.

1.    Resistance of conductor decreases.

2.    Resistance of semiconductor increases.

Since Copper is conductor its resistance decreases and resistance of germanium (semiconductor) increases here.