Question

Expression for capacity of parallel plate capacitor and energy stored by it

Answer 1

Considering a parallel plate capacitor of area A of each plate and K is the dielectric constant of the medium in between the plates.

Let σ be the charge density and Q is the charge stored in the plates.

σ= Q/A

Field strength that generated due to the

plates be, E= σ/Kε₀----- (1), where ε₀= free space permittivity  

Potential difference b/w the plates V= E.d,  where d is the gap b/w the plates.

V=  σd/Kε₀----- (2)

  Putting the value of σ in (2)

V= {(Q/A)d}/Kε₀= Qd/Kε₀A

We know that, Capacitance C= Q/V

So, C= Q/V=  Q/ (Qd/Kε₀A)

     C= Kε₀A/d