Which of the following statements are correct?

(A) Metals obey Ohms law at constant temperature.
(B) The resistivity of the metals depends on temperature.
(C) The conductivity of the metals is independent of temperature.
(D) The number of electrons per unit volume in a metal is independent of temperature.

Choose the correct answer from the options given below:

(A), (B) and (D) only

The correct answer is Option (1) → (A), (B) and (D) only

Correct Analysis:

(A) True: Metals obey Ohm's law as long as the temperature is constant. Ohm's law states that $V \propto I$, which is valid for most metallic conductors under constant physical conditions.

(B) True: The resistivity of metals increases with temperature due to increased lattice vibrations, which scatter the electrons more.

(C) False: Conductivity is the reciprocal of resistivity. Since resistivity increases with temperature, conductivity decreases. So, it is dependent on temperature.

(D) True: In metals, the number of free electrons per unit volume (electron density) is largely independent of temperature, because the electrons are already delocalized in the conduction band.