The electric field must be zero inside a conductor in electrostatic equilibrium, but not inside an insulator. it turns out thatwe can still apply gauss’s law to a_ gaussian su_rface that is entirely within an insulator by replacing the right-hand side ofgauss’s law, q5160, with qinie, when: 5 is the permittivity of the material- (technically, 60 is called the vacuumpermittivity.) suppose a long, straight wire with linear charge density 250 nc/ m is covered with insulation whosepermittivity is 2,550,. what is the electric field strength at a point inside the insulation that is 15 mm from the axis of thewire?