Discussion Forum

The capacitance of a parallel plate capacitor with air as a medium is 3 $\mu$ F. As a dielectric is introduced between the plates, the capacitance becomes 15 $\mu$ F. The permittivity of the medium C²N^-1 m^-2 is 

Answer:

Explanation:

 Capacitance  of air capacitor 

 $C_{0}= \frac{\epsilon_{0}A}{d}=3\mu F$  ....(i)

 whem a dielectric of permittivity $\epsilon_{r}$ and dielectric constant K  is introduced between the plates , then 

 Capacitance  ,  $C= \frac{k\epsilon_{0}A}{d}=15\mu F$  ...(ii)

 Dividing eq.(ii)  by (i)  , we get

 $\frac{C}{C_{0}}=\frac{d}{\frac{k\epsilon_{0}A}{d}} =\frac{15}{3}$

 $\Rightarrow$  K=5

 $\therefore$  permittivitty of the medium

 $\epsilon_{r}=\epsilon_{0}K$

 =  $8.85\times 10^{-12}\times 5=0.44\times 10^{-10}$