Though our homes have 15-amp and 20-amp branch circuits (and larger ones for specific appliances), the rating of a receptacle and the rating of a circuit it's installed on do not necessarily ...

Behind the wall, 15-amp outlets typically connect to 14-gauge wires, while a 20-amp uses thicker 12- or 10-gauge wires. These wires correspond to the amount of current each circuit can safely handle.