I'm not EE trained. I apologies for my ignorance.
I'm trying to understand AC electricity at the moment. But I'm very confused on how alternating current works. I've a hypothetical scenario here. An appliance, the bulb.
For eg. The first instance when we power on and electricity flows.. Live wire (230v) -> bulb (230v 3A) -> neutral wire( 0v 3A)
Am I correct if assuming I measure all 3 points with reference to ground?
I'm confused..
Please refrain from posting unnecessary replies. Reply only if you know the answers to below 4.
Can someone illustrate the full cycle. Using a bulb? Everyone is saying something different.
Here are the details.
1) we have 3 wires. earth. hot. neutral.
2) how does neutral conducts electricity when it's grounded at substation. Doesn't that short circuit?
3) why is neutral always 0v reference to earth? Even when there is a current flow from neutral to live in the half cycle?
4) how does neutral wire power the bulb in the second cycle when it is -230v 0A
1:
Only at the premises. The distribution grid is a different story and your mileage varies based on the applicable standards in each region.
2:
see the "DaveCAD" attached. The energy comes from the transmission lines via transformers. Transformer coil ends as such have no "live" or "neutral". They just have voltage
between the coil ends. No ground. No neutral. Just a voltage (AC) between the coil ends. Every half cycle the polarity of the voltage changes, but only in relation to the coil ends themselves, nothing else.
3:
"Neutral" only becomes "neutral" once it is explicitly tied to the ground using a physical conductor. Until that moment, it is just one of the transformer coil ends, floating free in the universe. The act of connecting a coil end to something references the coil potentials of those points. You could connect one coil end to the positive pole of a 400 V battery, and at that moment the coil end would be at +400V in relation to the - pole of that same battery. Measure the other coil end against the - pole of the battery, you would see your coil AC voltage + the constant 400 V of the battery. But
nothing else.
So when you ground one of the coil ends, it then
becomes the neutral by virtue of being connected to the "universal" neutral voltage, i.e planet earth. We all share that potential by being in galvanic connection to the planet, so that is why it is called "Neutral" or "Ground" - there is no potential
difference between points tied to a common point. For all we know, Earth could be charged to a potential of 10^12 V by the particles of the solar wind, but who cares since we all sit in that same potential. To us it is all equal and we can call it 0 if we want to (and we do).
4:
"Wires" don't power anything. Current circulates in a conducting loop (circuit) where there is a potential difference in one or more places. Thus the circuit you are thinking is made of: the step-down transformer supplying your house. That is the generator of the potential difference by virtue of magnetic induction in the transformer secondary, giving rise to the voltage in the secondary coil ends. The coil ends are brought into the house where the light bulb is then connected as the load between the wires. For convenience, there is the switch interrupting one wire when you want to sleep. So now we have a complete circuit: The voltage between the coil ends drives a current through the load via the connecting wires. The direction of the current at each instant is determined by the polarity of the voltage between the transformer coil ends. Since the transformer operates with AC voltages, the polarity and thus the direction of the current will alternate at 50 or 60 times per second, depending on where on the planet you happen to light your bulb.
Now, for several reasons i won't go into, it is usually considered a good idea to reference the above circuit to the ground potential. To get this effect, we simply tie one of the transformer coil ends physically to planet earth using a conductor. It makes no difference which coil end you select, because they are equivalent in this respect. You just pick one and that then becomes your "neutral". But note that it in no way influences the above circuit at all. The circuit is just referenced to earth potential (i.e. made same as) in one point, the node that became the "neutral".