As far as I know, Ohm's law (in macroscopic form) states that the in some devices/conductors/materials, the (instantaneous) current through the device is directly proportional to the (instantaneous) voltage across the device. It can be proven this occurs only if the (static/DC) resistance of the device is constant; if it is variable, then the voltage and current aren't directly proportional, so Ohm's law is not satisfied.
In the above, I haven’t discussed about temperature. In metallic conductors, as we know their resistivity is dependent on the temperature of the conductor, which depends on the ambient temperature and the current flowing through the conductor (Joule’s law). Since the resistance depends on the resistivity, it follows the resistance of a metallic conductor depends on the current through it. Doesn’t that make metallic conductors not obey Ohm’s law (since the voltage is not directly proportional to current)? Or am I wrong (if so, how)?
I read the following questions and corresponding answers, but they don’t address or answer my question:
- Ohm's law holds at constant temperature - what about Joule heating?: The question does address mine. The question and answer by Bill N say that temperature must be held constant in order for Ohm’s law to be satisfied. Is this true? I mean, if we change the current in a metallic conductor, the truth is its temperature will change and so its resistance will also.
- Do metals at low temperature follow Ohm's law?: The asker is asking regarding very low temperatures.
- Ohm's law in metals: The question does address mine. The answer by KF Gauss says that if temperature depends on resistance, it doesn’t contradict Ohm’s law. I think it does, as I explained above. I commented their answer but didn’t get a reply.
- Can Ohm's law break in metals?: The answers don’t seem to have addressed my question.
- Non-ohmic conductors: The answers don’t seem to have addressed my question.
- Ohm's law hold till what temp?: The asker is asking regarding very low temperatures.
- Ohm's law and Joules heating: The answer by BioPhysicist does address my question, and seems to be in agreement with what I said. Can anyone confirm if we’re correct?