Derive the expression for capacitance of parallel plate capacitor.
Let the two plates are kept parallel to each other separated be a distance d and cross-sectional area of each plate is A. Electric field by a single thin plate E′=σ2ϵo
Total electric field between the plates E=σ2ϵo+σ2ϵo
Or E=σϵo
Or E=QAϵo
Potential difference between the plates V=Ed
⟹ V=QdAϵo
Capacitance C=QV
Thus we get capacitance of parallel plate capacitor C=Aϵod