Step 1: Definition of Specific Conductivity (Conductivity).
Specific conductivity, also called conductivity (κ), is defined as the conductance of a solution contained between two electrodes having a unit area of cross-section and separated by a unit distance (1 cm). In simple terms, it represents the ability of a solution to conduct electric current.
Mathematically,
κ = (1 / R) × (l / A)
where R = resistance of the solution,
l = distance between electrodes,
A = area of cross-section of the electrode.
Unit of Specific Conductivity:
In SI system: Siemens per meter (S m−1)
In CGS system: Siemens per centimeter (S cm−1)
Step 2: Definition of Cell Constant.
The cell constant is defined as the ratio of the distance between the two electrodes (l) to the area of cross-section (A) of the electrodes.
Cell constant = l / A
It depends only on the geometry of the conductivity cell and remains constant for a given cell.
Unit of Cell Constant:
Since l is in cm and A is in cm2,
Unit = cm−1
(In SI system, it can be expressed as m−1)
Conclusion.
Thus, specific conductivity measures how well a solution conducts electricity and is expressed in S m−1 or S cm−1, whereas the cell constant is a geometric factor of the conductivity cell expressed in cm−1 or m−1.