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.