Electronics > Beginners
Need somebody to talk to about AC concept
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tester43:
Dear All,

Do not hate me for stupid questions please :)

I doubted myself - after building multiple projects using micro-controllers I give up and went back to read about basics (definition of voltage etc).

I have a lot of basic questions for AC current.
I am looking for somebody to have a conversation (patience needed).

To ask the first question: what's the concept of GND in AC.
In DC it's extremely easy - low potential + high potential = difference.
What's the meaning of GND symbol in AC circuits?
agehall:
GND is always just a reference point. You can pick it arbitrary. Doesn't matter if we talk about AC or DC. This took me a while to realise but the way I grasped the concept was to look at a battery powered circuit, placing the ground reference in various places to see how calculations were done and realising that the result was always the same.

Then it is just a matter of applying the same concept to all other circuits.
tester43:
In DC it's plan and simple. Just pick a point and go on. For example japanese devices in the past had GND at the level of a few volts above zero - to make issues analysis easier.
In the older times with first transistors GND was at the peak voltage - to make it more easy to calculate transistor point.

BUT with AC: you have 2 wires coming from transformer - what now :)
agehall:
Same principle. Pick one and say that is your ground reference. The other one is then relative to that reference.

I'm sure someone with much more AC experience will jump in and explain all about neutral and how that may (or may not) relate to ground in various countries, but in principle, ground is just a reference point you attach somewhere and everything else is then considered to be relative to that point.

To simplify, think about the battery powered circuit again. Now imagine that you (instantly) flip the battery around 50 times/second - all of a sudden you have AC.
tester43:
i was waiting for this.
So ... Neutral wire. But: when you are using the plug with 2 pins you can freely flip the sides so I can't assume which wire is neutral.

Hmm in a way you could use line as GND. In this way voltage would be the difference with neutral....
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