Option 1: This statement correctly explains Ohm`s law. According to Ohm`s law, the current flowing through a conductor is directly proportional to the potential difference (voltage) applied.

Option 2: This statement is also correct. Ohm`s law states that a conducting device obeys it when the resistance of the device remains constant regardless of the magnitude and polarity of the applied potential difference.

Option 3: This statement is correct as well. Ohm`s law applies to conducting materials when their resistance remains constant regardless of the magnitude and direction of the applied electric field.

Option 4: This is the incorrect statement in regards to Ohm`s law. Ohm`s law does not apply uniformly to all materials. Only certain materials, known as "ohmic" or "homogeneous" materials, obey Ohm`s law under certain conditions. Homogeneous materials exhibit a linear relationship between current and voltage, independent of the strength of the electric field or the presence of any other fields. However, certain materials like diodes and other non-linear elements do not follow Ohm`s law.

Alert - correct answer should be: 4