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After a recent post and watching several videos about AC circuits my understanding is better, however there is something I’m not sure on. Picture an AC circuit distributed to a household. I’m in the UK so let’s say 230 volts, with a frequency of 50hz. Now, the neutral is grounded, meaning close to earth potential. Why is the hot wire not at the same potential with only the load/loads separating the two? In the most recent video I watched the poster stated that it was the resistance of the load/loads that separated them and that if the neutral was magically cut then it would carry the same voltage as the hot wire, with respect to ground. The poster did not go in to any detail about how the load resistance affected this. Can some please explain to me what I’m missing?

Many thanks, Simon.

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Why is the hot wire not at the same potential with only the load/loads separating the two?

There has to be a potential difference across the load in order to deliver power to the load.

If both sides of the load were at the same potential (ground or any other potential) then no power would be transferred to the load.

So grounding the hot wire would defeat the purpose of building a big expensive electric power utility.

In the most recent video I watched the poster stated that it was the resistance of the load/loads that separated them and that if the neutral was magically cut then it would carry the same voltage as the hot wire, with respect to ground.

This is because if the neutral is cut, then no current can flow from hot, through the load, through the neutral and back to the generator (the source of power). If there's no current flowing through the load, then there's no potential drop across it. So that means the "neutral" is now actually hot. It's not grounded any more because you cut its connection to ground (I'm not sure about the UK, but in the US the neutral is typically bonded to earth ground at the breaker panel).

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  • $\begingroup$ Hi The Photon. Thanks for taking the time to comment. I’m still uncertain and perhaps you misunderstood me. I understand that you would not ground the hot wire as well as as you say this would not create a potential difference. My question was or should of been how is the hot wire not grounded as well? How does the grounded neutral not travel through the load and not ground the hot wire at the same time? I’m sorry for my ignorance $\endgroup$
    – Simon Baughurst
    Commented Oct 9, 2020 at 10:24
  • $\begingroup$ @SimonBaughurst, the load must have non-zero resistance (if it didn't we wouldn't transfer any power to it), and many also have non-zero reactance. This limits the current drawn by the load, and prevents it presenting a short-circuit to the generator. $\endgroup$
    – The Photon
    Commented Oct 9, 2020 at 16:13

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