If alternating current goes both ways, why do some plugs only allow you to put them in one way?

Question

If alternating current goes both ways, why do some plugs only allow you to put them in one way?

In: Engineering

Answer 1

The current flows both ways but only one of the prongs has *voltage* on it. In other words one side is neutral while the other side alternates between “pushing” and “pulling” the current in different directions.

So only one of them is dangerous if you touch it. The neutral would be connected to any outer shell or other part of the device you could touch, while the “hot” is not connected to anything you might touch.

This is not totally safe because it relies on the outlet having the hot and neutral switched, which is why some devices have 3 prongs. The third one is a neutral/ground and that type of outlet is less likely to be miswired so this is the best standard of safety.