Circular plate capacitor with different disks
  In this paper we write a system of integral equations for a capacitor composed by two disks of different radii, generalizing Love's equation for equal disks. We compute the complete asymptotic form of the capacitance matrix both for large and small distances obtaining a generalization of Kirchhoff's formula for the latter case. 
Giampiero Paffuti, Enrico Cataldo, Alberto Di Lieto and Francesco   Maccarrone
physics.class-ph