The charge supplied by a battery to a cylindrical capacitor of coaxial cylinders of radii 4cm and 6cm with length 1m to charge it to a potential of 4kV is:
If the capacitor is in the form of two conducting coaxial cylinders of radii r1 & r2(r1<r2) and length L, then the capacitance is C=2πϵLlnr2r1 where ϵ is the permittivity of the material filling the gap between the cylinders.
So the charge, Q=CV=2πϵLlnr2r1V
here, r1=4cm,r2=6cm,L=1m,V=4kilovolt,ϵ=8.85×10−12 for air.
∴Q=2×3.14×8.85×10−12ln64×4×103=0.548μC