Which of the following are correct statements?

A. The resistivity of a material is found to be dependent on the temperature
B. In metals number of free electrons per unit volume is not dependent on temperature.
C. Resistivity of semiconductors increases with increasing temperature
D. Resistivity of metal increases with increase in temperature

Choose the correct answer from the options given below:

A, B and D only

The correct answer is Option (4) → A, B and D only

(A) For metals, Resistivity generally increases with temperature while for semiconductors resistivity decrease with temperature.

(B) As the temperature increases, the number of free electrons can increase directly due to thermal excitation.

(D) This happens because, as the temperature rises, the atoms vibrate more, increasing the likelihood of collisions.