Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Alternating Current problem

Status
Not open for further replies.

e44-72

Member
Hello

I know from an ac generator on one half turn of the coil one of the wires from the generator will be posistive and the other negative and on the other half it will swap and the negative wire becmomes positve and the other negative.
I therefor can't understand how alternating current in our homes works as for example in a plug one wire is positve and other negative and a third wire which is ground. How is it then that the voltage alternates from +240 to -240 in the same wire while the negative wire stays at zero? why does it not alternate between both wires i.e one is +240 and other 0 then 0 goes to +240 and 240 to 0?

Can someone explain this. Thank you for any replies.
 
Last edited:
Well the reason that the neutral wire stays at zero is that it is connected to ground.

The generator (or the local transformer) produces an alternating between two wires. The voltage between them doesn't change if one or the other is connected to earth, so either connection, or even the mid point, can be grounded.

Power is transmitted on both the positive half-cycle and the negative half-cycle, so there is no disadvantage in having one live wire that is sometimes positive and sometimes negative. Having one wire near zero volts means that switches or fuses in the live wire will disconnect the power and make the circuit safe, when there are no voltages relative to ground.

If either wire is not earthed, isolators or switches have to be arranged to disconnect two wires not one, which makes them more complicated.

In situations where positive power only is needed, a bridge rectifier will give voltages that always positive. If a transformer winding is connected to a bridge rectifier, the two ends of a transformer winding will alternately go positive in the way you describe. That is done where DC current is need.
 
Thank you for your reply. I have been wondereing for ages why it is this happens and couldn't find the answer anywhere, I thank you for your response.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top