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Show that the magnitude of the polarisation of dielectric medium is equal to the surface density of bound charges induced on its surface? |
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Answer» <P> Solution :LET A be the area of cross section of dielectric slab and its thickness be d. Assume `pm sigma_(p)` to be the induced surface charge densities at the front faces of dielectric slab. Equal and opposite CHARGES appears on the front faces of dielectric slab, given by `Q=sigma_(p)A`. Electric dipole moment is charge multiplied with distance between the charges. Hence, the electric dipole moment developed can be WRITTEN as `sigma_(p)Ad`. Polarisation is electric dipole moment developed per UNIT volume. Hence, polarisation of dielectric medium is equal to the surface charge density of bound charges induced on its surface. `P=(sigma_(p)Ad)/(Ad)=sigma_(p)`. |
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