Coil shielding

[Bobman]

Can somebody explain why the copper fabric shielding (ie 3M) around a typical coil manages to effectively cancel spurious signals without cutting the very weak and much wanted return signals please?

[Carl-NC]

Coil shielding blocks the electric field component but not the magnetic field component. Target signals are purely magnetic while EMI is combined electric+magnetic, and capacitive effects are purely electric.

[Bobman]

Many thanks Carl, thought I'd ask before pouring epoxy all over my finished Arduino coil!