What is the mathematical relationship between the radius $(r)$ of a cylindrical conductor and its cross-sectional area $(A)$?

With dilution,the conductivity of a solution $—$

The molar conductivity for electrolytes $A$ and $B$ are plotted against $C^{1/2}$ as shown below. Electrolytes $A$ and $B$ respectively are:

What is the molar conductivity of $0.02 \text{ M}$ $KI$ solution if its conductivity is $4.37 \times 10^{-4} \text{ }\Omega^{-1} \text{cm}^{-1}$?

If the values of $\Lambda_{\infty}$ of $NH_4Cl$,$NaOH$ and $NaCl$ are $130$,$217$ and $109 \ ohm^{-1} \ cm^2 \ equiv^{-1}$ respectively,the $\Lambda_{\infty}$ of $NH_4OH$ in $ohm^{-1} \ cm^2 \ equiv^{-1}$ is:

The molar conductivity is maximum for the solution of concentration (in $M$)