U=21CV2=21dKϵ0AV2 where K is the dielectric constant
Electric field due to a point charge placed in an infinite dielectric
E=4πϵ0r2Kq where q is the point charge placed inside an infinite dielectric and r is the distance at which the electric field is calculated.
Dielectrics are non-conducting substances which are the insulating materials and are bad conductor of electric current. Mica, Plastics, Glass, Porcelain and Various Metal Oxides and even dry air is also example of dielectric.
Permittivity and relative permittivity
E=KE0 where K is the relative permittivity,Eis the resultant electric field and E0 is the applied electric field. The permittivity is ε=ϵ0K
Electric polarization of matter
Polarization occurs when an electric field distorts the negative cloud of electrons around positive atomic nuclei in a direction opposite the field. By inducing the movement of electrons within an object, one side of the object is left with an excess of positive charge and the other side of the object is left with an excess of negative charge. Charge becomes separated into opposites.The polarization process always involves the use of a charged object to induce electron movement or electron rearrangement.
The maximum electric field that a dielectric medium can withstand without breakdown (of its insulating property) is called its dielectric strength. For air, it is 3×106V/m This puts a restriction on the value of capacitance of a given size and is the reason why capacitors are in the range of μF.
n parallel plate capacitor, when dielectric slab is placed between the two plates then the ratio of the applied electric field strength to the strength of the reduced value of electric field capacitor is called dielectric constant that is: K=EEo K = Dielectric constant Eo=Dielelctric E = Net Field
Effect of dielectric on capacitance
The larger the dielectric constant, the more charge can be stored. Completely filling the space between capacitor plates with a dielectric increases the capacitance by a factor of the dielectric constant C = KC' Where C= New capacitance after introduction of dielectric C' = Capacitance with no dielectric between the plates.
Effect of electric field on dielectric material
Dielectric are non-conducting substances and have negligible number of charge carriers. When a conductor is placed in an external electric field, free charges move such that the net field inside the conductor is zero. This is not possible in a dielectric. In a dielectric, the electric field induces dipole moment by reorienting the molecules of the dielectric. This causes an electric field opposing the external electric field. Hence, the electric field inside a dielectric is smaller than the original electric field.
Properties of Dielelctrics
1. Dielectrics does not have any free charges. 2. When an electric field is applied there is small displacement of bound charges creating small electric dipoles within the dielectric. This phenomenon is called Polarization. 3. The electric field inside and outside a dielectric gets modified due to presence of dipoles. 4. Dielectrics can store energy.
If in any dielectric substance the centre of positive charge and centre of negative charge of each molecule do not coincide, then such type of dielectric material is called polar dielectric. Ex : water and HCl
If in a substance the centre of positive charge and centre of negative charge of each molecule coincide with each other, because of symmetry of molecules, then these substances are called non-polar dielectric substances. Ex: N2,O2,H2 etc.