Step 1: Understanding the formula.
The cell constant \( k \) is related to the electrical resistance \( R \), the cell length \( b \), and the conductivity. The cell constant \( k \) is defined as the ratio of the distance between the electrodes (length) to the area of the electrodes. The relation is given by:
\[
k = \frac{b}{R}
\]
Where:
- \( b \) is the length of the cell, and
- \( R \) is the electrical resistance.
Step 2: Analyzing the options.
(A) \( k = \frac{R}{b} \): This is incorrect because it does not accurately represent the relationship between the conductivity and resistance.
(B) \( k = \frac{b}{R} \): This is correct. The correct relation between the cell constant, conductivity, and electrical resistance is \( k = \frac{b}{R} \), where \( b \) is the cell length and \( R \) is the resistance.
(C) \( k = \frac{1}{R \cdot b} \): This is incorrect, as it does not align with the proper relationship.
(D) \( k = R \cdot b \): This is also incorrect.
Step 3: Conclusion.
The correct answer is (B) \( k = \frac{b}{R} \).