# Does electromagnetic shielding using conductor metal sheet enclosure attenuates magnetic field as well?

Does electromagnetic shielding using conductor metal sheet enclosure attenuates magnetic field of the electromagnetic wave as well? If yes, what is the relation? I know it does attenuate electric field of the electromagnetic wave.

A (electric) conductive sheet does not shield the magnetic field at all.

If you use an iron/steel sheet, which has a high magnetic permeability then it would reduce the magnetic field (which prefers to stay inside the iron/steel rather than go back outside again ;-)

You can get the situation where the magnetic field is created by the electric current, and by careful arrangement of the conductors you keep it's field totally inside the outer one. Coaxial cable being one case in point.

If you are getting interference from a magnetic field it is normal to use a high permeativity shield (iron , steel, Mu metal) or to add a ferrite core around the electric cable (the go/return pair) so that there is minimal induction into the cable.

In what context do you need to know (e.g. 'homework', electronic noise rejection, large magnetic field rejection, etc.)?

• But isn't the electric and magnetic fields related by some formula. So, if electric field amplitude goes down, so does the magnetic field?
– akm
Commented Jun 20, 2016 at 2:40
• @AmitMaurya, the problem is that the formulae are often presented at one frequency, and are about the EM wave transmits as a pair, rather than how the differnt frequency components may pass through differently. In addition the field curvature component is often ignored which can potentially over-simplify things. Most of the true formula relate the rate of change of one to the magnitude of the other, and vice versa, so the direct amplitudes are not related. (the earths magnetic field is everywhere (local flat earth perspective;-) yet it doesn't cause an electric field. Commented Jun 20, 2016 at 13:42
• If following relation is true in the context of emw - B=E/c, where symbols have usual meanings, then don't you think attenuation of electric field results in attenuation magnetic field as well?
– akm
Commented Jun 21, 2016 at 16:40
• Assuming "emw=electro magnetic wave", implying a far field plane wave, then yes, the PEC (Perfect Electrical Conductor) will reflect both the E and M field parts of the wave (at the impedance of the space), with a small eveanescant wave (skin depth decay) appearing to be transmitted through the PEC. My original reply was for separate M fields which were not particularly part of an EM wave. Commented Jun 21, 2016 at 19:38
• Thanks a lot for your reply. My question was in the context of emw. I realized my question was not clear about that. I corrected it now.
– akm
Commented Jun 22, 2016 at 2:18