Our Physics teacher used to tell us that in an ac circuit the current and hence the flow of electrons is reversed every half cycle as the polarity of the supply changes every half cycle. However I am still puzzled about the following. In the UK, the live is the wire that delivers electrical power from the power grid while the neutral is the return wire. If this is so does it mean that the flow of electrons is reversed in BOTH live and neutral wires every half cycle? Why does the direction of the current change if the live remains live while the neutral remains neutral all the time? Is there a good analogy to explain this concept better?