Ohm's law is not applicable to:

Explanation

All AC Circuits and Conductors obey Ohm's Law as the current flowing through them is directly proportional to applied voltage i.e a straight line for I-V graph but semi-conductors do not obey Ohm's Law as I-V graph is a curved line instead of straight line. Ohm's law is not directly applicable to semiconductors in the same way it is to metallic conductors. Semiconductors, such as silicon and germanium, exhibit non-linear behavior in terms of their resistance with changes in voltage and current. Their resistance can vary significantly with changes in voltage and temperature, and they typically do not obey Ohm's law over a wide range of voltages and currents.