In coulomb's law, on what factors does the value of electrostatic force constant K depend ?

In Coulomb’s law, on what factors the value of electrostatic force Constant ‘K’ depends ?

The value of electrostatic force constant in free space is ……… .

On what factors, does the value of electrode potential depend?

On what factors does the value of angle of contact depend ?

The electrostatic force between two charges is governed by Coulomb.s law. On which factors does the electrostatic force between two charges depend and how?