Capacitance with a Metal (conducting) Slab—

Let we have a capacitor of plate area ‘A’ and separation ‘d’ between the plates, then

Now, we place a metal slab of thickness ‘t’ in between the two plates of capacitor and the electric field in the conducting slab is zero. Hence, the potential difference between the plates is,

Capacitance with a Dielectric Slab—

Let we have a capacitor of plate area ‘A’ and separation ‘d’ between the plates, then

Now, we place a dielectric slab of thickness ‘t’ and dielectric constant ‘k’ in between the two plates of capacitor. Hence, the potential difference between the plates is,

Dielectric—

A dielectric is a type of insulator which has a property of polarization.

Generally, insulators are formed by covalent bonding, so, these elements do not have free electrons to conduct electricity. But the insulators which are formed by the atoms having large electro negativity difference, the shared electrons are shifted to the atom towards the high electro negative element. So, a small dipole is formed in a molecule. 

Parallel Plate Capacitor—

Parallel Plate Capacitor is the simplest capacitor which consist of two parallel conducting plates

Let we have a parallel plate capacitor which has two parallel conducting plate of area ‘A’ and placed at a small distance ‘d’. If +Q and –Q charges are given to both plates then,