Resistance (R) = Voltage (E) / Current (I)
At that time, the standards for Voltage, Current and
Resistance had not been developed. Ohm’s Law expressed the
fact that the magnitude of the current flowing in a circuit
depended directly on the electrical forces or pressure and
inversely on a property of the circuit known as the resistance.
Obviously, however, he did not have units of the size of our
present volt, ampere, and ohm to measure these quantities.
At this time, laboratories developed resistance elements,
constructed of iron, copper or other available alloy materials.
The laboratories needed stable alloys that could be moved
from place to place to certify the measurements under
review. The standard for the ohm had to be temperature
stable and with minimum effects due to the material
connected to the ohm standard.