Question

A parallel plate air condenser has a capacity ‘C’. When the plate separation is halved and a dielectric of constant k is inserted, new capacitance is found to be 12C. The value of dielectric constant ‘k’ is?

• A. 12
• B. 24
• C. 6
• D. 3

Answer 1

The correct option is C 6

$C=\frac{{ϵ}_{0}A}{d};C^1=\frac{k{ϵ}_{0}A}{\left(\frac{d}{2}\right)}$
$\frac{C^1}{C}=2k;$
$12=2k;k=\frac{12}{2}=6$