My microwave takes up an ungodly amount of space on the counter so it can reach a plug with a ground connector. I’d like to move it off the counter - but the outlet on that side of the room is old, and doesn’t have a ground. Can I safely use an electric ground adapter? It would be the only appliance connected to that outlet.
As long as the cover plate screw is actually connected to ground, this is an OK, if not great solution.
It would be better to re-wire the outlet with a proper grounding receptacle.
Some of the wiring in an older house of mine (built 1960’s) actually did have 3-wire power; the unshielded third or ground wire was connected to a ground screw on the electrical box. Since the outlet screws into that box, yes the screw in the midle of the outlet between the plugs was grounded.
What I did when I needed 3-prong for computers etc. was replace the 2-prong outlet with a 3-prong, ensuring that the ground wire was connected to the outlet ground. In some cases the wire reached and I transferred it ot the outlet. In other cases, there was not enough slack; I cut a short ground wire from the wiring box screw to the outlet ground screw. (Be sure it does not touch the live wires!!!)
If you don’t have the ground wire in your outlet box - not sure what to do.
You can plug anything into 2-prongs, but that adds to the risk that an electrical problem can cause the entire case (a metal outer box, I assume) to become live. The ground is just added protection. Also, if the wiring is backwards (wouldn’t happen, would it?) you could end up with the neutral actually being the live.
If you do plug it in and don’t shock yourself, odds are you are safe. However, in a room where water can be splashing all over the place sometimes, perhaps a small investment in proper grounding is worthwhile.