In household wiring, the wall outlet usually has a slot for a large prong and one for a small prong. This type of outlet is said to be “polarized”. The small slot is electrically “hot”; in a typical 115 volt system it oscillates 60 times a second between about +170 volts and -170 volts, compared to ground. To get a shock, it is necessary to touch this “hot” slot (or to touch something electrically connected to it), while also touching something which connects to ground. Things that are connected to ground include the larger “neutral” slot, the round “grounding” slot in a 3-prong wall outlet, plumbing pipes, and any metal which is part of a sink or bathtub.