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Electrostatics

Gauss Law

  • Inside a conductor, electrostatic field is zero. In static solution, the free charges have so distributed themselves that the electric field is zero everywhere inside.

  • At the surface of a charged conductor, electrostatic field must be normal to the surface at every point.

  • The interior of a conductor can have no excess charge in the static situation.

  • Electrostatic potential is constant throughout the volume of the conductor and has the same value (as inside) on its surface.

  • Electric field at the surface of a charged conductor is given by,

  • Electrostatic shielding − It is the phenomenon of protecting a certain region of space from external electric field.

Dielectrics and polarisation

  • Non-polar dielectrics − The centre of positive charge coincides with centre of negative charge in the molecule.

Example:

  • Polar dielectrics − The centres of positive and negative charges do not coincide because of the asymmetric shape of the molecules.

Non-Polar Dielectrics

  • When a non-polar dielectric is held in an external electric field , the centre of positive charge in each molecule is pulled in the direction of and the negative charge centre is pulled in a direction opposite to .

  • The two centres of positive and negative charges in the molecule are separated. The molecules get distorted. The non-polar molecule gets polarised or a tiny dipole moment is imparted to each molecule.

Polar Dielectrics

  • When no external field is applied, the different permanent dipoles of such a dielectric are oriented randomly. Therefore, the total dipole moment is zero…

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