# electricity ??

maxximus | 04:39 Fri 28th Jul 2006 | How it Works
in canada we use 240 volt, a ground 2 power wires red/black and a common or neutral white wire. then it is reduced to 120 by using only 1 of the power wires either red or black combined with the others. all lights and outlets or points as you call them are 120 and although you get a fair tingle in a mishap it is not life threatning. now are all lightbulbs in britain also 240 and if so, that would mean one could realisticaly lose there life changing a light bulb. being so easy to reduce it why wouldn't you. thanx!

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Yes all mains power is 240 volt in UK, when you are blessed with a little intelligence you avoid sticking fingers in light bulb sockets and if you are really intelligent you could also turn the switch off first, its not a problem I have ever come across. generally speaking a 240 volt shock is not a big a problem, unpleasant, yes! hurts, yes! very unlikely to kill you but it does happen.
Its perfectly easy to die of electric shock from 120V, let alone 240V. The key issue is the current (amps) flowing through the body, not the voltage experienced. The current flowing is dependent on the resistance to the electricity down to earth potential (ground) which is where the current flows to. So if you have clammy fingers, and are stood bare-foot in a pool of water, the resistance down to earth in any situation is much lower, and the current is larger. This is why in the UK, at least, there are all sorts of additional regaulations placed upon the use of electricity in bathrooms. The regulating body in the UK (the IEE) calculated that a 'safe' voltage, under which one would never expect to die from shock is just under 30V.
Power, in watts, is given by the formula "voltage, multiplied by the current in amps". If you double the voltage, you obtain the same power with only half the current. With a reduced current, you can use thinner wires to conduct the electricity. Think of all the wiring in all the houses and businesses throughout the country - using a higher voltage adds up to a huge saving in raw materials.
You may have come across some electrical items for the kitchen, 'Made in Japan', and wondered why they have such thick and heavy cables attached. The mains voltage in Japan is only 100 volts, so the cable has to be able to take a correspondingly higher current.
Question Author
thank you ratter, you may be soley responsible for saving my life down the road, although my point was by going to 120 there is no need for a switch at the outlet. i understand your point about amperage heathfield but i don't get how it relates to raw materials. here once it is brought to the main panel in the home, major appliances, stove, dryer some shop tools are powered by an 8 gauge or no smaller than 10 gauge 4 strand wire. all other fridge, washer, hot water tank, furnace etc. including all outlets and lights are powered by small sometimes 12 but usually 14 gauge 3 strand wire which is less raw material on the whole. if i'm understanding your point. most appliances have as small as 16 guage and lamp chord for lighting is thin 18 guage. so being as a wire has to be run to any point that needs power, i am still not clear on why you would use a more dangerous power source at a point like a light bulb. are ther many instances of people suffering serious shock in their home, or are british people raised to be a little more fearful and respectful of electricity, or is it more to do with european market as apposed to north american market with the regards to the sale of large and small appliances. thanks for you replies cheers!
The method you describe for halving the voltage in Canadian homes works presumably because you have a two phase supply, each phase being 120 volts. In the UK the supply is single phase 240 volts, so simply connecting the ground and one of the other wires would not produce the same result. In the UK the other wires are Live and Neutral (the neutral wire is grounded at the transmission point, so the only voltage between ground and neutral will be that caused by resistance in the transmission system (generally this amounts to a few volts). On the other hand the voltage between the gound and the live wire will be of the order of 240 volts (depending again on resistances with in the system)
Question Author
yes we use single pole breakers(single phase) and double pole breakers(2 phase) at the transmission point or panel as we call it. i didn't know you only used single phase but it can be split using a double pole breaker. so my question still hasn't been answered. i have been curious about this for years, so can anyone give me a clearer understanding? and thanks for your answer roger wilco.
Hi Maxximus. To answer your question... The reason we don't reduce it is because the whole country is fully wired with a single live wire at 240 volts. There is no second phase. Imagine asking all of Canada to reduce their 120 volts lamp fittings to 60 volts, and you'll see what I mean.
Houses in the UK carry the power for all domestic appliances like washers, driers, electric kettles, etc through the house to the room power outlets via single stranded cables. The wires have no AWG gauge equivalent, but at 1.7841 mm diameter they lie between AWG 13 and 14. This wire is rated at about 20 amps. Normally, all the appliances mentioned will have a fuse rated at 13 amps contained wthin the plug on the appliance's connecting cable. This allows for a 3 kw appliance to be run from that single strand cable.
If the same appliance was to be run on 120 volts, at 3 kw you'd be using 25 amps to get the same power. This is why you have like a AWG 14 gauge three strand cable - requiring almost three times the raw material (copper) than the UK cable uses. Hence my previous remark.
Question Author
heathfield my good man, thanks for your patience. as they say 'the light has gone on' i have seen wiring as you describe but not with the fuse built into the plug, this is why your plugs appear so large, and country wide and as you correctly state that is a lot of extra raw material. one more if you don't mind, comparing the two, along with the obvious advantage in the amount of material used are there any other obvious advantages/disadvantages, and is it going to cost me the same as you to run that 3kw appliance , i'm assuming yes. i am not an electrician but have a half decent grasp of the basic's. cheers eh!
(1) Hi Maxximus. Since we're all charged by the electric companies for the power we use in watts, then if your tariff and my tarriff were the same for each watt, we'd be charged an equal price for running our 3 kw appliance.
As to advantages and disadvantages of higher versus lower voltage, well, at a higher voltage it's not just the house wiring that can be thinner wire, but also the wiring inside electric motors, like for your washer and dryer, allowing them to be smaller and lighter. Even down to the heating elements in your toaster and kettle, and the filaments in lamps. Economy all round!
(2) Also, all wires have resistance, however slight, and this causes a power loss. One of the formulae for power is 'Power in Watts = volts squared, divided by the resistance'. If you increase the voltage, you reduce the power loss, and the power companies are very aware of this. It's the reason why tranmission lines operate at thousands of volts.
3) Safety? Well, power tools on UK construction sites now have to operate on 110v. Otherwise, we're taught about the dangers of electricity at an early age, and in the Europe-wide 220/230/240v system, there aren't too many accidents.
4) Edison started off offering a three-wire d.c. system of +100v,-100v, and 0v (earth). I've read that he didn't understand a.c. too well, didn't like it, and it was his employee Tesla who developed it. 120v a.c. was chosen as it has the same heating effect on a resistor as 120v d.c. He reckoned 60Hz was most efficient, though in Europe this was reduced to 50Hz just so as to simplify calculations in metric! (Any lower in frequency, and you start to see flicker in lights).
Sorry about the multi-paragraph reply, but AB was having a go-slow this morning, and I couldn't post it in a one-off.
Question Author
again, thanks for your patience heathfield. i thought as much on the 3kw appliance and your points on economy all round make good sense. the power loss due to resistance is referred to as line loss here and as you say the power company has it factored in. i still think i would be a little learier changing a light bulb there than at home though as we are taught to respect electricity from young but with a lot more emphasis put on 240 or 220 as it is commonly called here as being 'deadly'. even though a lot of our larger appliances, compressors, etc. run on it. my dad was a signal maintainer on the railroad for years and the whole system is d.c. and he always stated in his opinion, was a better system but my understanding of it is not as solid as his. i have read a bit about tesla and my understanding is he did not get the full credit due to him and had some theories that are most interesting but too detailed to get into here. so thanks again for your most detailed answers, cleared up a lot of questions for me, much appreciated cheers again eh!
Can I just point out that in the UK electricity is distributed as 50Hz 3 phase. 400V phase to phase and 230V phase to earth(actually 415V & 240V) roughly speaking the three phases are split over three properties. Hence industrial premises can be supplied with 400V.
Acknowledged, Pottsy, though there are plans afoot to reduce these voltages to harmonise with the electricity supplies in other EU countries.

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