In the years 1825 and 1826, Ohm did his work on resistance and in 1827 published his results. From Fourier’s work, he drew considerable inspiration on heat conduction in the theoretical explanation of his thesis. He initially for experiments, used voltaic piles, however later used a thermocouple as it provided in terms of internal resistance and constant potential difference a more stable voltage source.

As published by Ohm the law specifically applied to his experiments with conduction in metallic wires. Later, when electronic circuits were created that needed a broader range of resistances in a compact form. From nonmetals resistors were assembled that obeyed Ohm’s Law. Nonmetallic and metallic resistors are called ohmic devices, because they obey Ohm’s Law, at least within certain limits of current and voltage.

The resistance outside these limits, of an ohmic device varies with the current and voltage. Eventually, the device, at extremely high voltages,  may agonize from electric breakdown, causing a short circuit; or at high currents, the device might melt due to overheating, leading to an open circuit.

Named after its discoverer George Ohm, Ohm’s law,  states that the potential difference between two points along a connected path and the current flowing through that path are proportional at a given resistance. The potential difference is termed as the voltage drop from one point to a other within the connected path of a conductor. Ohm is the unit of resistance, which is equal to one volt second per coulomb or one volt per ampere .