Which one of the following statements regarding Ohm’s law is not correct?

Ohm’s law is an assumption that current through a conductor is always directly proportional to the potential difference applied to it.

A conducting device obeys Ohm’s law when the resistance of a device is independent of magnitude and polarity of applied potential difference.

A conducting material obeys Ohm’s law when the resistance of material is independent of the magnitude and direction of applied electric field.

All homogeneous materials obey Ohm’s law irrespective of whether the field is within range or strong.