Can a neon indicator light work across L and N?

[Penners]

At least that's better than the Waveries - they steal your electricity.

Thanks for the explanation about voltage, Zebra. Please can you (or someone) now explain the difference between earth and neutral to me? As I understand it, neutral is bonded to earth anyway, in a protective multiple earth system. So I don't understand the difference between the two.

 

[philpjuk100]

Neutral is blue,earth is green and yellow!

 

[Zebra]

Well yes, they end up in the same place, but the neutral is intended as a return path for the current being used, whereas the earth is simply a safety conductor, giving a path for a fault current to flow back to the substation, when a fault occurs, so that the fuse or breaker will trip. It would be bad if you mixed neutral and earth up within an installation because a neutral, although not live, can still give you a shock if you got in it's way, ie took a neutral conductor out and touched it when there's a load on it, whereas earth should never have a current on it unless there's a fault, and then only for a very short time. Within the installation you don't really want your washing machine casing, metal light fittings etc connected to neutral, which is carrying the circuit's current under normal conditions.
There is such a thing as an earth-free location, an installation without an earth, and if I remember correctly there is such a thing as an installation with neutral and earth combined, but they're very rare, for specific uses, and I've never worked on either.

 

[Penners]

Thanks Zebra.

My late mother-in-law was convinced that, if you left a socket switched on without a plug in it, the electricity would leak away.

Seems reasonable to me.

 

[Flyfisher]

If the switched live was not connected to anything then nothing would happen when it was switched on would it?
When the switch is off, the 'switched live' side is connected to Neutral through the lightbulb.

Sorry, you're right, I was thinking without the load connected, ie without the lamp in.

In which case, you'd be right of course - the neon wouldn't light. Tricky things forums, for the non-telepathic, anyway. :wink:

Incidentally, our two scenarios demonstrate how a neon across a switch can be used to indicate a lightbulb failure. When the lamp is switched on it's obviously working. When switched off, the neon will light only if the lightbulb is intact. But if the neon is not illuminated when the lightbulb is off, then it means the bulb has failed.**

Not sure how useful that actually would be in the real world, but there we are. :lol:



** Purists may point out that it could also mean the neon has failed, which would be true but, compared to the relative lifetimes of neon and normal bulbs, fairly unlikely.

 

[Zebra]

Impractical, as you say, but creative, I like it.