Hi Mousri,

if I understand your question correctly, and you are asking about a (quasi-) static electric field: The magnetic nature of the metal doesn't change anything. The external field will cause a charge distribution on the surface of the metallic object in such a way that the external field is completely compensated by the field of these charges in the inside of the object, i. e. inside the metal, the resulting field is zero.

Inside the insulator, the external field will either generate electrical dipols, or existing dipols will be (partly) aligned to the field. Generally, the superposition of the external field and the field of the dipols will result in a field which is weaker than the external field.

Depending on the direction of the external field relative to the interface, the charge density at the surface of the metal at the interface might be higher than without the insulator.

Hope this helps.

If we apply an varying electric field then what happen?

Is it possible that because of this varying field an induced magnetic field will occur , and paramagnetic effect will occur....

I am just trying to clear my concept@Joerg Fricke

A varying electric field is always accompanied by a varying magnetic field (as described by the Maxwell equations). At very low frequencies, the magnetic field will be slightly stronger inside the metal due to its paramagnetism. Since generally, with increasing frequency the penetration depth of the field into the metallic object is decreasing (skin effect), here are two effects working in contrary directions.

Generally, an interface between an insulator and a conductor acts as a guide for electromagnetic surface waves. The propagation speed of such waves depends on the thickness of the insulating layer as well as on the permittivity and permeabilitiy (= 1 in most cases) of the insulator.

I guess if

a) the penetration depth is relatively large (low frequency or high resistivity of the metal), and

b) the insulating layer is thin,

then the propagation speed of surface waves will slightly decrease with increasing permeability of the metal.

If the layere is thin, then the penetration depth is automatically larger, right!!!

But I can't understand that why you say at low frequency the magnetic field will increases ? as we know that f is proportional to B.@ Joerg Fricke

Sorry, but no, the penetration depth decreases with increasing conductivity, permeability, and frequency. It does not depend on the thickness of the metal or the insulator layer.

What I tried to say is that paramagnetism is defined by a relative permeability > 1 but not as large as in ferromagnetism, and consequently a larger B occurs for a given H, but that only at low frequencies the H and B fields will completely penetrate the metallic object (depending on size and shape of the object). So (for a given H field) at low frequencies we will have a larger magnetic flux inside the metal while at high frequencies the flux will mostly be driven out by the metal.

@ Joerg Fricke : thank u so much sir for giving this information.

But if i feel another problem about this I will ask you.......