In 1825, Georg Simon Ohm, then a physics teacher in Cologne, described experiments to determine the electrical conductivity of metals. He investigated this using a setup whose measuring device was derived from Coulomb's torsion balance. The torsion balance consisted of a metallic thread with a magnetic rod inserted into an elderberry pulp cylinder at its end. During the experiment, an electric current runs through a copper wire below the magnetic rod. The resulting magnetic field deflects the magnetic rod, and the torsional force required for the reset serves as a measure of the electromagnetic interaction.

The two ends of the wire from the torsion balance were immersed in vessels containing mercury. One of the vessels also contained a wire from the copper-zinc element, which served as a voltage source. The second wire from the battery went into a third vessel containing mercury. Wires of different lengths were used for the measurement, connecting the third vessel to the second vessel and thus closing the circuit.

With his setup, Ohm concluded that the conductivity in the wires and deflection of the needle are dependent of one another by a logarithmic law. He revised this theory a year later, also based on further experiments with a setup in which the voltage was provided by a thermocouple.