# When a dielectric slab of thickness 6cm is introduced between the plates of parallel plate condenser, it is found that the distance between the plates has to be increased by 4 cm to restore the capacity to the original value. The dielectric constant of the slab is

Capacitance

$C=\frac{\epsilon_0A}{d}$

Capacitance when a dielectric of thickness t is placed between the plates

$\dpi{100} {C}'=\frac{\epsilon _{0}A}{d-t+\frac{t}{k}}$

Given when the separation between plates is d+4,  C'=C

Therefore

$\dpi{100} \\\\\frac{\epsilon _{0}A}{d+4-t+\frac{t}{k}}=\frac{\epsilon _{0}A}{d}\\\\\text{implies}\\\\d+4-6+\frac{6}{k}=d\\\text{implies}\\\\k=3$

### Preparation Products

##### JEE Main Rank Booster 2021

This course will help student to be better prepared and study in the right direction for JEE Main..

₹ 13999/- ₹ 9999/-
##### Rank Booster NEET 2021

This course will help student to be better prepared and study in the right direction for NEET..

₹ 13999/- ₹ 9999/-
##### Knockout JEE Main April 2021 (Easy Installments)

An exhaustive E-learning program for the complete preparation of JEE Main..

₹ 4999/-
##### Knockout NEET May 2021

An exhaustive E-learning program for the complete preparation of NEET..

₹ 22999/- ₹ 14999/-