Limitations of Ohm’s Law

There are various limitations of the Ohm’s Law, some of which are as follows:

• Ohm’s law is not applicable to unilateral electrical elements like diodes and transistors as they allow the current to flow through in one direction only.
• For non-linear electrical elements with parameters like capacitance, resistance, etc. the voltage and the current won’t be constant with respect to time making it difficult to use Ohm’s law. Non-linear elements are those which do not have current exactly proportional to the applied voltage, which means the resistance value of those elements changes for different values of voltage and current. Examples of non–linear elements are thyristors, electric arcs, etc.
• The relation between V and I depends on the sign of V(+ or -). In other words, if I is current for a certain V, then reversing the direction of V keeping its magnitude fixed, does not produce a current of the same magnitude as I in the opposite direction. This happens for example in the case of a diode.
• Ohm’s law is only applicable to metallic conductors. So it won’t work in the case of non-metallic conductors.

Ohm’s Law is a relationship between three physical phenomena: current, voltage, and resistance. This relationship was introduced by German physicist George Simon Ohm. That is why the law is well known as Ohm’s law. It states that the amount of steady current through a large number of materials is directly proportional to the potential difference, or voltage, across the materials. Thus, if the voltage V (in units of volts) between two ends of a wire made from one of these materials is tripled, the current I (in amperes) also triples; and the quotient V/I remains constant. The quotient V/I for a given piece of material is called its resistance, R, measured in units named ohms. Although, Ohm’s Law is valid to a large extent however it has some limitations. In this article we will learn in detail about Limitation’s of Ohm’s Law and its applications with having some brief introduction about the basics of Ohm’s Law.