Four materials that do not obey ohms law of resistance

Here are four materials that do not obey Ohm's law of resistance:

1. Semiconductors: Materials like silicon or germanium, especially when doped and used in devices such as diodes and transistors, exhibit a non-linear relationship between voltage and current. Their resistance changes significantly with applied voltage or temperature.
2. Gases: When gases are ionized (e.g., in a discharge tube or fluorescent lamp), their resistance is not constant. The current flow is highly dependent on the applied voltage and the ionization process.
3. Electrolytes: Solutions containing ions (like salt water) do not always obey Ohm's law, especially at higher current densities or when electrochemical reactions occur at the electrodes, which can introduce non-linear effects.
4. Tungsten (in an incandescent bulb): The resistance of tungsten wire increases significantly as its temperature rises due to the passage of current. This means the current-voltage relationship is not linear, as the resistance itself changes with the current.