SCALING RELATION FOR THE INDUCTANCE OF A COIL ON A FERROMAGNETIC HALF-SPACE

The calculated change in inductance when an air-core coil is placed ne xt to a uniform ferromagnetic half-space is found to be well described by a simple two parameter scaling relation for a broad class of coils . The scaling relation is Delta L(omega) = Delta L0L (omega/omega(0)) . Here, Delta L-0 is a constant that determines the overall strength o f the inductance change, while the frequency scale is set by omega(0), the frequency for which Re Delta L(omega) is zero. We test the hypoth esis that the inductance change of a coil next to a uniform ferromagne tic plate can be described by the scaling relation with measurements m ade on a suite of medium carbon steels. (C) 1997 American Institute of Physics. [S0021-8979(97)00821-9].