why electric field can never be tangent to perfect conductor

[goodtime]

dielestric

in dielectric and conductor interface (electric wall)
assuminf perfect conductor

why electric field can never be tangent to a perfect conductor
( nxE=0)

and why magntic fiels can never be normal to a perfect conductor
(n.B=0)

any one can help me plz

 

[subharpe]

why tangential field+conductor+is zero

Electric Feld:

If there is a tangential electric field just outside the metal, according to boundary conditions, the equal tangential electric field should exist just inside the metal too.
Now if there is a tangential electric field inside the metal, the line integral of this between any two points on the surface of the metal should give the voltage drop while going from one point to the other. But in a perfect conductor, there should not be such voltage drop as it is assumed to have infinite conductivity. Therefore the tangential electric field component just inside and just outside the metal should be zero, i.e.electric field should be normal.

Magnetic field:

Magnetic filed lines have to close the loop. If they don't bend outside the metal, i.e. if they are perfectly normal to an interface the boundary condition say, just inside the metal also there should be only perpendicular magnetic field, notangential component. In that case, to bend the magnetic field line where does the tangential component arise from? Because inside the metal any plane perpendicular to the field line can be assumed to be n interface where also BC must hold, and as on one side, only perpendicular compnnt exists, on te other sid also only the normal component can exist and this continues along the thickness of the metal. In a nutshell, a normal component cannot give rise to a tangential component. Then where is the source for tangential component. There must be tangential component outside the metal which continues inside too, to allow bwnding of the field line.

So magnetic fied cannot be perpendicular to metal-dielectric interface inside the metal.