How the force acting between two charges will change if the air medium betweeen them is replaced by metalic plate?

A force of 4N is acting between two charges in air.If the space between them is completelly filled with glass (epsilon_(r)=8) then the new force will be

The force between two point charges in air is 100 N. If the distance between them is increased by 50%, then the force between two charges will be nearly equal to

The force between two point charges in air is 100 N. If the distance between them is increased by 50%, then the force between two charges will be nearly equal to

The force acting between two point charges in vacuum is 10 N. If the charges are placed in a medium of relative permittivity 5, then the force acting between them will be—

How does the force between two charges change , if the dielectric constant of the medium in which they kept , increases ?

The capacitance of a parallel plate capacitor having air between its plates is 10 mu f . if the distance between the plates is reduced to half and the medium between plates is replaced by a medium of dielectric constant k=5 , then find the value how much increase or decrease in the capacitance of the capacitor.