Test: Electrostatics of Dielectrics - JEE MCQ

The microfarad (symbolized µF) is a unit of capacitance, equivalent to 0.000001 (10 to the -6th power) farad. 

A polarized dielectric is equivalent to two charged surfaces with induced charges (polarization charges). 

The dielectric constant of metal is infinite as the net electric field inside the metal is zero.

• The dielectric constant is defined as the ratio of the permittivity of a substance to the permittivity of free space.
• As the electric flux density increases, the dielectric constant increases.

• Polar molecules occur when two atoms do not share electrons equally in a covalent bond.
• The oxygen side of the molecule has a slight negative charge, while the side with the hydrogen atoms has a slight positive charge.
• Ethanol is polar because the oxygen atoms attract electrons because of their higher electronegativity than other atoms in the molecule.

 The extent of polarization of dielectrics depends on the relative strength of two mutually opposite factors - the dipole potential energy tending to align the dipole with the external field and thermal energy tending to disrupt the alignment.

As charges are separated on the surface of the dielectric but not in its interior volume.

• When an external electric field is applied to the conductor, the free electrons in the conductor move in an opposite direction to that of the applied electric field.
• This movement of electrons induces another electric field inside the conductor which opposes the original external electric field.
• This continues until the induced electric field cancels out the external field. 

The electric dipole moment per unit volume is called polarization or polarization density (vector p). It is always directed from negative charge to positive charge.

The displacement of charges inside the dielectric stops when the external force on the charges of the molecules is balanced by the force due to internal fields.

The external electric field polarizes the dielectric and an electric field is produced.
The net electric field inside the dielectric decreases due to polarization.