Silence and now AC

How does AC electricity work?

A few apprentices have over time have asked me to explain how AC works, since they comprehend how DC works. They know that you need a flow of electrons around circuit which is sent from the negative terminal of a battery and returns to the positive terminal. They know that these electrons are capable of heating up metal to such an intensity that it produces visible light. Again they also know that the heated metal is found inside light bulbs.

So when asked about AC they know that electrons flow first in one direction and then all goes in reverse and the electrons flow in the opposite direction etc. The problem is that they cannot understand how the circuit is made.

In order to explain how AC works I have then asked them to look at the old fashioned steam train and how the piston moves backwards and forwards and yet creates a movement in one direction. The piston pushes out and turns the wheel, as it pulls back it continues to turn the wheel in the same direction.

So once they understand how a backwards and forward motion can be converted to a movement only in one direction, it is then time to look at railways again. So we now look at a super long train and a big powerful locomotive at one end. The locomotive will only move a few yards in either direction however.

I then point out that it is not the content of the wagons making up the train that is important it is the actual movement backwards and forwards that is important. A secondary reason for using the train is to explain how the relatively slow electron can create electricity at the speed of light. When the locomotive shunts into the trucks/wagons you can hear each collosion as the wagon/truck hits the next and so on. Imagine how long it would take from the first truck/wagon being shunted until the last one gets shunted. Even if the train went from the UK to the USA, it would not take long before a shunt in the UK would be heard in the US.

The apprentice can now translate the locomotive and associated train into electron flow in an electrical circuit and how their backward and forward movement can still produce a linear effect.