Four identical capacitors each of capacity C are connected across the vertices of a square ABCD as shown. The ratio of minimum and maximum equivalent capacities possible across any two vertices is

Try to find equivalent capacities between the pairs (P, Q) (P, R) and (P, S). This will give all possible equivalent capacities.

maximum between P and Q  C+C/3=4C/3

and minimum between P and R  $\frac{C}{2}+\frac{C}{2}=C$