A metallic conductor is subjected to a steadily increasing potential difference while its temperature is kept constant.
(i) Define resistance and state the mathematical relation connecting the potential difference across a conductor and the current through it.
(ii) Describe how the nature of the V–I graph helps you decide whether the conductor obeys Ohm’s law.
(iii) Explain why the same conductor may cease to obey Ohm’s law when it is allowed to heat up appreciably, even though its material remains unchanged.