Electromagnetic Induction in a Conducting Sphere with a Concentric Shell


  • James R. Wait,

  • Kenneth P. Spies


A quasi-static derivation is outlined for the problem of a shell-enclosed homogeneous solid sphere immersed in a slowly varying electromagnetic field. The secondary magnetic potential is expressed as a zonal harmonic series whose terms are proportional to a complex multipole response function xn of order n. The frequency dependence of the real and imaginary parts of xn is demonstrated to have diagnostic features related to the geometry and to the electric properties of the core and the shell.