Dumb Question....

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If you touch a live conductor to a neutral it goes bang so why when you plug a bulb in to a light and the current runs up the live , through the bulb and back down the neutral (which I understand is the case) why doesnt the same occur?? Presumably the bulb has completed the circuit??

Also if power runs back down neutral where does it go??

D
 
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Because the lamp has a resistance.

The 'short' is the lamp filament which glows as the electricity passes through it.

Resistance is like squeezing a hosepipe.

The harder you squeeze the hosepipe (increase the resistance) the less water (current) will flow through it.

If you connect live directly to neutral with no fuses in the circuit at all the cable will heat up until it is glowing (like the lightbulb filament), but the cable will get so hot it will melt (and probably set fire to whatever it is touching).

The lightbulb filament is inside a glass bulb filled with an inert gas to prevent the filament just burning away which it would if in contact with oxygen.

All metals have a resistance per CSA per meter, some much higher than others. (Some none metals will too)


Hope that makes sense
 
Yes, but where does the electricity going down the neutral go?

(Apart from into the carpet... ;) )
 
securespark said:
Yes, but where does the electricity going down the neutral go?

(Apart from into the carpet... ;) )

This was obviously the dumb part of the question - but..... where does it go???

Just checked the carpet and its definitely not there !!! :LOL: :LOL:
 
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dunny said:
Also if power runs back down neutral where does it go??

D

As a simplistic description the AC power in the home is distributed from a local transformer.This transformer has a winding (a coil of wire).From each end of this winding comes 2 wires, 1 phase, 1 neutral.These 2 wires come to your home and finish say at the lamp circuit via switches and fuses.Plugging in a lamp completes a continuous circuit.As there is a continuous circuit, current can flow (backwards and forwards as it is AC) as an alternating voltage is being induced (transferred) into the transformer winding by magnetic principles from the transformer primary (high voltage winding)
The neutral end of the secondary (low voltage) winding is earthed at the substation so that is why you will not normally receive a shock from a connected supply neutral.

This is also the reason that a fault from live to earth will short circuit as you are effectively shorting to neutral via the earthing methiod used.

Sorry if I'm waffling :oops:
 
dunny:

in reality no body actually know what currant is, many will argue they do, but no one is really sure, scientific models do change. We use a model to understand it the model we use are electrons flowing, and current is the rate of flow of the electrons.

this is analogous to water been pumped round a circuit, the faster its pumped is like more current, the higher the horse power of the motor is like a higher voltage.

people get confuse at this point and say 'if you cut a hose the water runs out' but in that model the air is the conductor where as we usually use air as an insulator. so breaking the circuit and cutting the hose the hose should be capped (ie an insulator put on the end) then no water flows just as no current would flow.

edit: just seen riccles answer, i forgot about AC my response is better tailored to DC, its easier to understand DC first.
 
Whoooshh!! Think I got most of that but its obvious that there is no simple answer!!

Cheers

D
 
dunny said:
securespark said:
Yes, but where does the electricity going down the neutral go?

(Apart from into the carpet... ;) )

This was obviously the dumb part of the question - but..... where does it go???

Just checked the carpet and its definitely not there !!! :LOL: :LOL:

You obviously have no idea.

electricity, is made from electrons, electrons come from, oh, see for your self click me
 

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