Two metallic plates of radius r are placed at a distance d apart and its capacity is C . If a plate

English

Gujarati

Hindi

2. Electric Potential and Capacitance

hard

The two metallic plates of radius $r$ are placed at a distance $d$ apart and its capacity is $C$. If a plate of radius $r/2$ and thickness $d$ of dielectric constant $6$ is placed between the plates of the condenser, then its capacity will be

A

$7C/2$

B

$3C/7$

C

$7C/3$

D

$9C/4$

Solution

(d) Area of the given metallic plate $A = \pi r^2$
Area of the dielectric plate $A' = \pi \,{\left( {\frac{r}{2}} \right)^2} = \frac{A}{4}$
Uncovered area of the metallic plates
$ = A – \frac{A}{4} = \frac{{3A}}{4}$
The given situation is equivalent to a parallel combination of two capacitor. One capacitor $(C')$ is filled with a dielectric medium $(K = 6)$ having area $\frac{A}{4}$ while the other capacitor $(C'')$ is air filled having area $\frac{{3A}}{4}$
Hence
$ = \frac{{{\varepsilon _0}A}}{d}\left( {\frac{K}{4} + \frac{3}{4}} \right)$$ = \frac{{{\varepsilon _0}A}}{d}\,\left( {\frac{6}{4} + \frac{3}{4}} \right) = \frac{9}{4}\,C$

Standard 12

Physics

Share

Similar Questions

A parallel plate capacitor with plate area $'A'$ and distance of separation $'d'$ is filled with a dielectric. What is the capacity of the capacitor when permittivity of the dielectric varies as :

$\varepsilon(x)=\varepsilon_{0}+k x, \text { for }\left(0\,<\,x \leq \frac{d}{2}\right)$

$\varepsilon(x)=\varepsilon_{0}+k(d-x)$, for $\left(\frac{d}{2} \leq x \leq d\right)$

hard

(JEE MAIN-2021)

Two parallel plate capacitors of capacity $C$ and $3\,C$ are connected in parallel combination and charged to a potential difference $18\,V$. The battery is then disconnected and the space between the plates of the capacitor of capacity $C$ is completely filled with a material of dielectric constant $9$. The final potential difference across the combination of capacitors will be $V$

hard

(JEE MAIN-2022)

The capacity of an air condenser is $2.0\, \,\mu F$. If a medium is placed between its plates. The capacity becomes $ 12\, \,\mu F$. The dielectric constant of the medium will be

easy

The radii of the inner and outer spheres of a condenser are $9\,cm$ and $10\,cm$ respectively. If the dielectric constant of the medium between the two spheres is $6$ and charge on the inner sphere is $18 \times {10^{ – 9}}\;coulomb$, then the potential of inner sphere will be, if the outer sphere is earthed……..$volts$

medium

A parallel plate capacitor filled with a medium of dielectric constant $10$ , is connected across a battery and is charged. The dielectric slab is replaced by another slab of dielectric constant $15$ . Then the energy of capacitor will ………………….

hard

(JEE MAIN-2022)