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 collom l farad= 1 volt (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 Q 4T∈0 so the capacitance gIven by C=Q/V=4丌o0R