Energy density in capacitor

 

1) We know energy store in a capacitor is



2) Now charge  Q = A σ

Where σ is the surface charge density

A  is the surface area



3) therefore


Again capacitance


 

Now putting the value of Capacitance C on 2.61 we get.







 

Now the volume of the capacitor is = A d

Therefore energy density is





Again we know electric field



Now putting the value of σ  in energy density equation, we get