Ohm’s law states the relationship between voltage, current and resistance. According to this law, the amount of electricity passing through a conductor between two points in a circuit is directly proportional to the voltage across the two points, for a particular temperature.
Ohm expressed his idea in the form of a simple equation, E = IR, which describes the interrelation of current, voltage, current and resistance. According to this algebraic expression, the voltage (E) across the two points is equal to current (I) multiplied by resistance (R).
Ohm's Law is a very helpful and simple tool for electric circuit analysis. It is widely used in the study of electrical circuits, resistive circuits, electronics, hydraulic analogy, reactive circuits with time-varying signals, linear approximations, temperature effects and heat conductivity.
Techopedia explains Ohm's Law
Ohm's law was discovered by German physicist Georg Simon Ohm. The law was published in his 1827 paper, "The Galvanic Circuit Investigated Mathematically."
Material obeying the principle of Ohm's Law is called linear or ohmic because the potential difference measured between two points varies linearly with the electric current. Gustav Kirchhoff reformulated Ohm’s law as J = sE, where J is the density of current at a given location in a material having resistance, E is the electric field at that particular location, and s is the conductivity, which is a parameter that depends on the material.
Ohm's law is generalized after a lot of experiments on materials that proved the direct relationship of the current with the electric field associated with the materials. Ohm’s law may not hold true all the time. Experiments have proved that some materials behave in a non-ohmic way when weak electric field is applied to them.
Early on, it was believed that Ohm's law would not be unsuccessful at the atomic scale. But later, researchers proved that Ohm's law is applicable for silicon wires with a width of only four atoms and a height of only one atom.