Quote:
Originally Posted by Radio Wrangler
Screening happens through conductivity. Conductivity simply shorts electric field components. Conductivity allows alternating magnetic field components to create circulating eddy currents and the mag field from these currents cancels the arriving mag field on one side, and creates a reflection on the other.
No conductivity, no screening.
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There are also magnetic shields made of magnetic material with a high initial permeability. They act as a low reluctance medium for the path of the magnetic flux, diverting it away from the space to be shielded. Often these are used to minimize mag fields getting into audio transformers or unwanted deflection of CRT beams, which is why many scope CRT's have Mu metal shields. If amazingly good shielding is required, two or three concentric shields will do it. This type of shield also makes for a good electrostatic shield too.
Pretty well any conductor makes a good electrostatic shield though, and you can have a good electrostatic shield, without a magnetic shield, if the shield is not a closed loop, like those used between a primary and secondary of a power transformer where the ends of the foil are insulated (or they would make a shorted turn).