Question

A parallel plate capacitor is charged upto 100V. A 2mm thick insulator sheet is inserted between the plates. Then to maintain the same potential difference, the distance between the capacitor plates is increased by 1.6mm. The dielectric constant of the insulator is:

• A. 6
• B. 8
• C. 5
• D. 4

Answer 1

The correct option is C 5

$x=1=[1-\frac{1}{k}]$
$1.6=2[1-\frac{1}{k}]$
$\frac{1}{k}=1-0.8$
$=0.2$
$k=\frac{1}{0.2}=5$