Test: Electrostatics of Conductors Dielectrics and Polarisation (November 14) - NEET MCQ

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

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.

 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.

• 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 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.

Electric field at A is different from field at B because, E= K/r²​
we know that conductor is an equipotential surface, so potential will be the same at A and B.
As charge density, σ∝1/r​, then charge density is different at A and B.

The electric field is zero inside a conductor Because the net charge inside a conductor remains zero , the total charge of a conductor resides on its surface , as charges want to attain equilibrium so they come on surface , to minimize the  repulsion among them .As the  charge inside a conductor is zero therefore , if we apply Gauss' theorem to find the electric field inside a conductor , we find it zero .

Since the electric field inside the conductor is zero and has no tangential component on its surface, therefore, no work is done in moving a test charge within the conductor or on its surface. It means the potential difference between any two points inside or on the surface is zero. Hence, electrostatic potential is constant throughout the volume of the charged conductor and has the same value on its surface as inside it.

When there is potential difference across the conductor, the electric field is set up. Due to this charge will flow across the conductor. But when conductors have the same potential the charge will not flow from one conductor to the other.