What are the conditions under which ohm's law is obeyed?

Answer 1

When you are using semi conductors or the conductor is at a very high temperature.

Answer

Ohm's Law is not a universal law, and only applies to a limited range of conductors. For Ohm's Law to apply, the ratio of voltage to current must remain constant for variations in voltage; if the ratio varies, then Ohm's Law does not apply. Materials for which Ohm's Law applies are called 'linear' or 'ohmic'; those for which it doesn't apply are called 'non-linear' or 'non-ohmic'. There are far more 'non-linear' materials than there are 'linear'; these include the metal tungsten, electrolytes, gases, and semiconducting devices, such as diodes, etc.

The ratio of voltage to current is termed 'resistance', and applies to both linear and non-linear devices. However, the equation, R = E/I, does NOT represent Ohm's Law; it is derived from the definition of the ohm. This equation applies for both linear and non-linear devices. But, for non-linear devices, it only applies at a particular voltage, as the ratio varies with changes in voltage.