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

AC is a wave. Picture a skipping rope – wiggle it so it goes up and down in the same place – a standing wave. Which way the wave is moving is meaningless – but you are wiggling it from one end, not both. Similarly, one wire is providing the power, but the wave is wiggling in both directions.