The magnetic screening effect of iron tubes

The magnetic screening effect of cylindrical iron tubes of different thicknesses and permeabilities is discussed and analysed, particular attention being paid to the effect of saturation. The problem is approached from a consideration of the induced pole strength on the surface of the iron. The distribution of pole strength is expressed by means of a Fourier series, and it is shown that such a distribution will, in general, cause a magnetic field which varies from place to place in the screened region. Values of the theoretical screening ratio are calculated and good agreement is observed with values obtained experimentally.