How do you pass a wire through the firewall of a jeep tj?

By power wire, I assume that you are talking about an amp or another accessory to that sort. You will have to look up behind your brake pedal toward the corner, there should be a small hole cover...

either drill a hloe thru firewall or use a screwdriver to make a hole in a rubber grommet that is already in firewall. then push wire thru . u dont need a big screwdriver and the rubber will close...

Yes, it can.

Through one of the gromets. Its a rubber stopper that has wrapped wires already going through it and looks like one of your drain plugs in the floor pan. Add what you need by puncturing a smaller...

Oh yes, electricity passes through wires. That is, in fact, the usual reason for having wires. Although wires can also be used to hang paintings.