Remarks (1) The physical meaning of C is the amount of charge needed to rise the potential by a unit(volt). In SI unit, C has the unit farad coulomb I farad U0 (2)Although C has been defined to be Q/V, it actually depends only on the size and shape of the conductor Example 1. isolated spherical conductor of radius R If it has a charge Q on it, then the potential is 4丌∈ 0 so the capacitance is given by C=Q/V=4丌oR