The materials and devices do not obey Ohm's law when

(A) The relation between V and I is not unique, i.e., there is more than one value of V for the same current I
(B) The relation between V and I depends on the sign of V
(C) V ceases to be proportional to I
(D) The relation between V and I is linear

Choose the correct answer from the options given below:

(A), (B) and (C) only

The correct answer is Option (2) → (A), (B) and (C) only

Ohm's law states that $V \propto I$ for a material/device. A material or device does not obey Ohm's law if:

(A) The relation between $V$ and $I$ is not unique — more than one value of $V$ for the same $I$ → violates Ohm's law.

(B) The relation depends on the sign of $V$ → violates Ohm's law.

(C) $V$ is not proportional to $I$ → violates Ohm's law.

(D) The relation is linear → obeys Ohm's law, so this is not a violation.

Non-Ohmic behavior: (A), (B), (C)