how does resisitivity increases or decreases with temperature in conductors , semiconductors ?
how does resisitivity increases or decreases with temperature in conductors , semiconductors ?
As answered previously...
Hi, Resistivity of conductor according to Lorentz-Drudge theory is given by
Where Ï = resistivity, me = mass of electron, n= no. of electrons/charge carriers per unit volume, t = relaxation time, e = electronic charge.
Now, in a conductor 'n' remains constant with change in temperature. Thus, Now if temperature increases, collision frequency increases thus relaxation time (i.e. time an electron remains without suffering a collision) decreases. Thus, Ï increases.
Thus, in general, electrical resistivity of conductors increases with temperature.
But in semi-conductors which are actually Si or Ge atoms connected by covalent bonds with each other, with a rise in temperature the covalent bonds collapse and a lot of holes/ free electrons increase. Thus n (ie. no. of electrons per unit volume) increases massively compare to decrease in relaxation time t.
In this case: Thus Ï increases with rise in temperature in semi-conductors.
As answered previously...
Hi, Resistivity of conductor according to Lorentz-Drudge theory is given by
Where Ï = resistivity, me = mass of electron, n= no. of electrons/charge carriers per unit volume, t = relaxation time, e = electronic charge.
Now, in a conductor 'n' remains constant with change in temperature. Thus, Now if temperature increases, collision frequency increases thus relaxation time (i.e. time an electron remains without suffering a collision) decreases. Thus, Ï increases.
Thus, in general, electrical resistivity of conductors increases with temperature.
But in semi-conductors which are actually Si or Ge atoms connected by covalent bonds with each other, with a rise in temperature the covalent bonds collapse and a lot of holes/ free electrons increase. Thus n (ie. no. of electrons per unit volume) increases massively compare to decrease in relaxation time t.
In this case: Thus Ï increases with rise in temperature in semi-conductors.
