A number of condensers, each of the capacitance 1 $\mathrm{\mu }$F and each one of which gets· punctured if a
potential difference just exceeding 500 V is applied, are provided. An arrangement suitable for giving
capacitance of 2 $\mathrm{\mu }$F across which 3000 V may be applied requires at least

Minimum number of condensers in each row $=\frac{3000}{500}=6$

If C_s is capacity of 6 condensers in a row,

                    $\frac{1}{{\mathrm{C}}_{\mathrm{S}}}=\frac{1}{1}+\frac{1}{1}+\frac{1}{1}+\frac{1}{1}+\frac{1}{1}+\frac{1}{1}=6$

$\Rightarrow {\mathrm{C}}_{\mathrm{S}}=\frac{1}{6}\mathrm{\mu F}$

Let there be m such rows in parallel.

Total capacity $=\mathrm{m}\times {\mathrm{C}}_{\mathrm{s}}$

                     $2=\mathrm{m}\times \frac{1}{6}$

$\therefore$                 m = 12

Total number of capacitors = 6 $\times$12 = 72