Fundamentals · 5 min read

Difference between electric and magnetic shielding

A grounded metal sheet stops an electric field almost perfectly and a 50 Hz magnetic field almost not at all. The confusion between the two costs projects dearly.

Electric fields are easy

Any grounded conductive surface terminates an electric field. Building materials, walls and even vegetation provide substantial attenuation, which is why electric fields rarely drive shielding projects at low frequency.

Magnetic fields are not

Magnetic fields pass through concrete, brick and most metals with little effect. Only high permeability or significant induced currents change their path.

Practical consequence

If a supplier proposes a simple metal foil or grounded mesh against a 50 Hz magnetic field problem, the proposal is physically unsound.

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