I am curious for many days that if i have a very thick sheet between very weak magnetic field say horseshoe magnet or electric field so flux would pass through them completely or gets block somewhere if yes then how does line of forces travel.
Is there any calculation for it to determine that for particular thickness the flux would pass effectively.
Dear Ahmed,
The change of the magnetic or electric field progates by the speed of light in the material between the source and the point of observation.
Best wishes
Antti
Well, the previous answer should be completed with index of refraction, isn't it?
On the other hand you can't hear radio when residing in a Faraday cage, so the things are not so straightforward. Many years ago, at some NATO conference related to magnetism, somebody reported that in a submarine, after changing position (or just orientation) it took some half an hour to observe a new, stabilized magnetic field inside. Some call this phenomenon magnetic viscosity. Yes, it takes some time to get a bulk material magnetized. I have no information concerning the behavior of (quasi)static electric fields, but I wouldn't be surprised to hear about similar "viscosity" in ferroelectric materials.
Thank you, Marek for very interesting information!
Besides, a soft magnetic material like mu-metal can be used for shielding against static magnetic fields. I misunderstood Ahmed's question in the first place.
Best wishes
Antti
The penetration of an electric field or a magnetic field in a material is determined by the penetration or skin depth.
It is given by the relation delta= sq. root (roh/ pi f0 Mu),
where roh the resistivity of the material , f0 is the frequency of the incident magnetic field, Mu is the permeability of the material.Mu= Mu0 Mur, Mu0 is the absolute permeability and Mur is the relative permeability.
As you see it depends on the electric and magnetic properties of the material.= in addition to the frequency of the field.
Best wishes
That's true, of course, but Ahmed's question concerned static fieldthe . The skin depth for f0 = 0 would be infinite
I think concerning the static magnetic field screening of the magnetic field emanating from a magnet is that one can complete the path of magnetic field lines from the north pole to the south pole by a high permeability material such that one introduces an easy magnetic path to the field lines. This material can be made to connect the north pole to the south poles. The space outside the magnetic material will be be more or less free from the magnetic field.
Best wishes.
The investigations of demagnetization processes by D\"oring (~1960) lead to the conclusion that magnetization spontaneously changes with time as M(t) ~ M(t=0) - S log t for over 4 decades of t expressed in seconds, for finite t (but not too small). It is a slow decay, slower than polynomial, and thus no specific time scale can be uniquely defined (note that in the given formula the log argument is not dimensionless as it should be). This is purely phenomenological observation and I don't recall to see any successful theoretical approach to this observation. One thing is sure: this is a manifestation of tendency to thermodynamical equilibrium. Bulky ferromagnet is a very complicated system, very far from 'ideal gas' picture, with various time- and orientation-dependent interactions between its subsystems, like magnetic domains, defects, inclusions, and so on. Even the shape of magnetic hysteresis loop looks differently when observed when the frequency of exciting field is changed. On the other hand, in very small ferromagnetic samples, their spontaneous magnetization changes as 'telegraphic noise', flipping up and down in unpredictable moments but many times during 1 microsecond.
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