Why has DIYNOT got a electrics forum?

[Softus]

Where the lower voltage is dangerous over the higher voltage is the increased FIRE hazard the higher currents present. The lower voltage results in higher currents as we all agree, however the size of conductor become even more critical then, as does the voracity of joints. Even the slightest error will produce serious heat, and in the right environment the chances of fire increase dramatically.

Sorry if I haven't read some earlier post properly, but it was difficult wading through the bickering.

These higher currents - why do they arise? Is it because a tool, say, of a given power consumption requirement, requires more current to achieve the same power when the voltage is reduced?

If so, then I can see an increased risk of fire, but the risk of a fatal electrical shock is reduced, surely? My reasoning here is that any human contact with 115V will result in a lower current than the contact with 240V, if all other conditions are the same.

Personally I think the European and certain Asian countries choice of 230V is about right when all factoirs are taken account of.

And Canada too!

Regarding the question over the use of the word INDUCE...without sounding condescending, I don't mean to be, I would suggest that perhaps you guys look the word up in a dictionary. Whilst I accept it is not technically correct, it is certain gramatically correct within English.

Induce has many meanings depending on how it is used, as many words in English are...how else would you describe the current created by the resistance of the circuit...??

I didn't need to look it up, because I already know the meaning, but here we go anyway...

in·duce Pronunciation Key (n-ds, -dys)
tr.v. in·duced, in·duc·ing, in·duc·es

• 1. To lead or move, as to a course of action, by influence or persuasion. See Synonyms at persuade.
  2. To bring about or stimulate the occurrence of; cause: a drug used to induce labor.
  3. To infer by inductive reasoning.
  4. Physics.
  • 1. To produce (an electric current or a magnetic charge) by induction.
    2. To produce (radioactivity, for example) artificially by bombardment of a substance with neutrons, gamma rays, and other particles.
  5. Biochemistry. To initiate or increase the production of (an enzyme or other protein) at the level of genetic transcription.
  6. Genetics. To cause an increase in the transcription of the RNA of (a gene).

To answer your question, about how I would describe the relationship between current and resistance, I wouldn't ever say that the current is created by the resistance. If anything can be said to create the current then the honour must surely fall to the potential difference between two points. A current will always result from this, and the amount of current is determined by both the voltage applied and the resistance of the circuit.

To say it induces it is not the same as INDUCTANCE..if you see my point...

Yes, I do see appreciate the difference between the two.

I still haven't read anything that explains why you think that sticking a human across a break in a neutral conductor will somehow result in the current otherwise flowing in the unbroken circuit then flowing through the human. This seems utterly wrong to me, but you've implied it more than once.

 

[keyplayer]

If your not a sparky, get your work checked!

Eh? Why? What was this thread about again?

 

[Big_Spark]

BAS..the courses you mentioned, from what I have heard about them..which is not a lot to be honest...would be the type of course I was thinking of...

Softus...The problem is that both Voltage and Resistance determine current, so any comment about which "causes" it in isolation of the other factors involved...however when discussing this , it is not easy to adequately explain things without getting too technical..I've been trying to avoid that as it is apparent that there are those here that would lose the essence of the converstion in that case.

I'm glad you understood my point about Induce and inductance...

Regarding the Neutral break..it is a simple electical fact. If the voltage or Potential difference is sufficient, then current will flow, so if the circuit is energised, but inactive due to a break, if something conductive "bridges" that break, a potential difference will exist across it, as such a current will flow which will be the product of a combined total of the resistances forming that circuit.

 

[Softus]

Softus...The problem is that both Voltage and Resistance determine current, so any comment about which "causes" it in isolation of the other factors involved...

I partly agree, but mostly don't. Here's why.

A circuit can have resistance, without either a voltage present or a current flowing, although of course the resistance can't be actively measured without applying a voltage. However, a circuit cannot have current flowing without a voltage. Therefore, whilst it is true that both V & R are factors in determining the value of the current, it is not accurate, at any level, or in any context, to say that the resistance either creates or induces the current.

...however when discussing this , it is not easy to adequately explain things without getting too technical..I've been trying to avoid that as it is apparent that there are those here that would lose the essence of the converstion in that case.

Point taken - perhaps a purely technical discussion would be appropriate for another topic.

Regarding the Neutral break..it is a simple electical fact. If the voltage or Potential difference is sufficient, then current will flow, so if the circuit is energised, but inactive due to a break, if something conductive "bridges" that break, a potential difference will exist across it, as such a current will flow which will be the product of a combined total of the resistances forming that circuit.

I agree with this, although I'm not sure it's necessary to expand the electrical vocabulary to include words such as "energise" and "bridge", when "live" and "connection" are perfectly fine and commonplace words. But I'm just being picky.

However, I'm not sure whether or not you still believe this:

...there is a significant difference between a shock from Phase to earth, where the current flowing in your body will be determined by your body's resistance, as for any electrical circuit, BUT if you complete a circuit by making the connection ACROSS A BROKEN NEUTRAL, then the shock you recieve will be the current flowing in the circuit at that time..you will effectively become part of the circuit rather than a seperate circuit..(as with a Phase to neutral or Phase to earth shock)

As I've previously said, and this is a point that I think you haven't answered:

I think you're implying that current has a kind of momentum; as if receiving an electric shock is like standing in front of a moving car - the faster the car the greater the injury. I don't think it works like that, but I'm forever open minded.

I feel that you might be recoiling from that statement having realised the fallacy of its content. This is what worries me - I take it that you're in the trade of working on electrical installations, so how is it that you could have made this statement in the first place?

 

[Spark123]

IMO one of the confusing terms used was "full load current". In a series circuit, current flowing is related to the pd and the sum of resistances of the circuit. In my terminology, full load current is when the circuit is in full operation hence pulling maximum current i.e. a motor under full load. Having a broken neutral will, in this case introduce firstly an open circuit hence no current should flow. If a person comes in contact with this break, in effect bridging the broken neutral, the person will be in series with the load resistance hence as there are now two resistances, full load current won't flow.

 

[Softus]

I agree with you Spark123, and am delighted that you've managed to put it so much more succinctly than me

 

[oilman]

My, I have missed a lot of goings on here. I have 3 points:

Sorry to throw a spanner in the works so late in the game, but voltage is not a hazard in itself, nor is current. Many of us have had a belt from a car ignition system. Give or take 45,000 volts, which will give rise to quite a few amps. The killer is power or more specifically Wh, since this is the energy. Alright, you might be able to stop a heart, or muck-up it's function with a very small amount of energy, but then cell destruction can be achieved with 10mW.

As for Bright-spark's authoritarian idea of stopping people doing diy electrics, who the hell does he think he is? IF YOU WANT TO STOP PEOPLE BEING KILLED, FIRST STOP GEORGE BUSH DOING ANYTHING AS DEATH SEEMS TO BE HIS TRADE, AND SECOND LOOK AT ROAD DEATHS. AM I GETTING THROUGH? Just don't tell ME I can't do my own wiring. I am confident from what you have written here I know more than you.

115V will not give rise to twice the current in a circuit that 230V will. It's just that you need twice the current to achieve the same power output.

 

[Bazdaa]

If your not a sparky, get your work checked!

Eh? Why? What was this thread about again?

Nothing to do with this!

Bazdaa

 

[Thermo]

And this ladies and gentlemen is why sparkies work on their own, and why you should never let more than one in your house at the same time. they can never agree on anything, so god knows how two of them would wire up your house working together.

sparky 1 I was wiring it according to thingys law

sparky 2 oh no you shouldnt do that what about do daas law

sparky 1 no you shouldnt listen to him look heres my calculations

sparky 2 ah but have you considered the 3rd quarter of the moon in all that

etc

etc

etc

 

[keyplayer]

don't tell ME I can't do my own wiring

Hear hear.

 

[Igorian]

My, I have missed a lot of goings on here. I have 3 points:

Sorry to throw a spanner in the works so late in the game, but voltage is not a hazard in itself, nor is current. Many of us have had a belt from a car ignition system. Give or take 45,000 volts, which will give rise to quite a few amps. The killer is power or more specifically Wh, since this is the energy. Alright, you might be able to stop a heart, or muck-up it's function with a very small amount of energy, but then cell destruction can be achieved with 10mW.

As for Bright-spark's authoritarian idea of stopping people doing diy electrics, who the hell does he think he is? IF YOU WANT TO STOP PEOPLE BEING KILLED, FIRST STOP GEORGE BUSH DOING ANYTHING AS DEATH SEEMS TO BE HIS TRADE, AND SECOND LOOK AT ROAD DEATHS. AM I GETTING THROUGH? Just don't tell ME I can't do my own wiring. I am confident from what you have written here I know more than you.

115V will not give rise to twice the current in a circuit that 230V will. It's just that you need twice the current to achieve the same power output.

Actually, on the secondary, the current is quite low, so it hurts, but you generally live (and hopefully don't do it again )

 

[oilman]

Actually, on the secondary, the current is quite low, so it hurts, but you generally live (and hopefully don't do it again )

It isn't if you want the same power out of it. W=EI, so if you half the volts you need to double the current.

 

[Softus]

Sorry to throw a spanner in the works so late in the game, but voltage is not a hazard in itself, nor is current. Many of us have had a belt from a car ignition system. Give or take 45,000 volts, which will give rise to quite a few amps. The killer is power or more specifically Wh, since this is the energy. Alright, you might be able to stop a heart, or muck-up it's function with a very small amount of energy, but then cell destruction can be achieved with 10mW.

oilman, I think there are two points here...

1. Current causes tissue heating, aka burning, which can be fatal. A small but sustainable voltage, that generates sufficient current capable of burning, can, of course, lead to death, but the current is the important attribute of this type of electrocution.

2. Current can interfere with the heart muscle tissue, causing fibrilation or even seizure.

The above is information given to me by a SRN.

Regarding a belt from the HT circuit on a 4-stroke petrol engine, the inherent circuit resistance is very high, even excluding that of the human body, so there is little chance of a fatal current being passed through the body.

As for Bright-spark's authoritarian idea of stopping people doing diy electrics, who the hell does he think he is? IF YOU WANT TO STOP PEOPLE BEING KILLED, FIRST STOP GEORGE BUSH DOING ANYTHING AS DEATH SEEMS TO BE HIS TRADE, AND SECOND LOOK AT ROAD DEATHS. AM I GETTING THROUGH? Just don't tell ME I can't do my own wiring. I am confident from what you have written here I know more than you.

Extremely valid point. I surmise that Big_Spark is indignant that others, who have not received his level of professional training, are still allowed to work on electrical installations.

 

[Igorian]

Actually, on the secondary, the current is quite low, so it hurts, but you generally live (and hopefully don't do it again )

It isn't if you want the same power out of it. W=EI, so if you half the volts you need to double the current.

But you haven't halved the volts, you've induced (correct usage ) a voltage many times that of the primary, and so current will be less (cos u can't get more power out than you put in). It's the primary that has high current, but at low voltage (12). The primary also has a low resistance, in the region of 1-2 ohms. The secondary uses thousands of turns of very thin wire resulting in a high resistance (thousands of ohms).

 

[jbonding]

this is one of the reasons i dont even venture to electrics, i went there with a question a long time back and got the responce the original poster is talking of "what the hell are you touching it for,leave it alone,Your stupid, pay me all your money attitude". i agree electric can kill and if you drink enough paint that will also kill you and if you fall down a hole or off a roof that might kill you. You could even get run over at the builders merchants, so theres plenty of ways of dying (wether you knew the time place and whatever lol).should this thread still be in general chat?when does the thread get moved to electrics?