Three plates A, B, and C each of area 50  cm2 have separation 3 mm between A and B and 3 mm between B and C. The energy stored when the plates are fully charged is

There are two capacitors in parallelPotential difference between A and B is 12V.   Potential difference between B and C is also 12V.  Now, C=ϵ0Ad=8.85×10−12×50×10−43×10−3=1.475×10−11 UAB=UBC=CV22=1.475×10−11×1222=1.06×10−9  Total energy stored,  2×1.06×10−9=2.12×10−9J