How many volts is dangerous?
VOLTS
- Thread starter ebee
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B
breezer
it doesn't work like that. (how many volts is dangerous)
the following is in "leymans terms"
its the current that kills you
voltage is measured in volts.
voltage is the potential difference between two points.
its the current that kills you
Current is measured in amps (less than an amp is milliamps, as millimetres are to centrmeteres)
resistance is measured in ohms
resistance is "how hard to get from point a to point b"
The currrent that can kill you is said to be around 20 mA
to get 20mA to flow through an object (or you) it depends on the resistance of said object
if the object has a high resistance then more voltage will be required to drive the current through
equaly if the object has a low resistance it will need less voltage to drive drive the required current through
you can reduce the contact point resistance by making something wet, so if you having a bath your resistance is lower than when you are not in a bath (as in if you are dry or wet) equaly if you measure the resitance between say your dry hands it will be higher than when they are wet.
also if the resistance is high and the voltage is high the object carrying the current gets hot (thats how electric heaters work, you must have noticed the element glowing orange, that is the element getting hot as it has a high resistance)
similarly bad connections also have a high resistance, theses can also get hot causing fires
lets take a 10kw shower for example
it should have a 10mm cable now if you used a 1 mm cable the resistnace would be too high and the cable would heat up, melt and cause a fire (that is why we get worried on these forums, people do not realise the consequences of what can go wrong)
its actually how fuses work, too much current and the fuse wire melts breaking the circuit
You may also like to know that if the voltage is high enough it will actualy fry what ever it is passing through, so that is why you sometimes hear of people suffering from from burns when they get an electric shock.
Gruesome but true:
people who are sent to the electric chair are often fried due to their resistance rather than electrocuted.
Also the higher the voltage the more it can "jump" so that is why "overhead lines" are so high up, so they cant jump to you, which is why you should NEVER climb a pylon, because as you get near it the electricity will jump to you and.........say no more.
a typical pylon runs at 33,000 volts although some are higher and some lower . The household supply is only 230v and a battery is only 1.5 v, so you can see the major difference.
ac or dc (alternatiing or direct current)
In short alternating current keeps changing direct current does not
if you touch an alternating current it puts your muscles into spasam (tingles) and if you touch a wire it will "throw you"
if you touch a dc current it will "hold" your muscles and keep you there, so you may also die of suffocation since your muscles can not move (you can't breathe) that is why your house supply is ac not dc as although both will kill ac is slightly safer. not to mention it is easier to "transport" ac across the country as opposed to using dc. (another "useless" thread later maybe)
Please remember the above although true does not go into the exact details and principlas of what is involved, it is just a basic outline.
so remember if you are not sure ASK or better still get a qualified electrician, not some one who "knows a bit" as what they do is probaly dangerous.
Earthing and rcd's etc are also not mentioned as you didn't ask and it would have made this post even longer. but in very short terms
anything metal must be earthed for saftey sake unless it is double insulated
the following is in "leymans terms"
its the current that kills you
voltage is measured in volts.
voltage is the potential difference between two points.
its the current that kills you
Current is measured in amps (less than an amp is milliamps, as millimetres are to centrmeteres)
resistance is measured in ohms
resistance is "how hard to get from point a to point b"
The currrent that can kill you is said to be around 20 mA
to get 20mA to flow through an object (or you) it depends on the resistance of said object
if the object has a high resistance then more voltage will be required to drive the current through
equaly if the object has a low resistance it will need less voltage to drive drive the required current through
you can reduce the contact point resistance by making something wet, so if you having a bath your resistance is lower than when you are not in a bath (as in if you are dry or wet) equaly if you measure the resitance between say your dry hands it will be higher than when they are wet.
also if the resistance is high and the voltage is high the object carrying the current gets hot (thats how electric heaters work, you must have noticed the element glowing orange, that is the element getting hot as it has a high resistance)
similarly bad connections also have a high resistance, theses can also get hot causing fires
lets take a 10kw shower for example
it should have a 10mm cable now if you used a 1 mm cable the resistnace would be too high and the cable would heat up, melt and cause a fire (that is why we get worried on these forums, people do not realise the consequences of what can go wrong)
its actually how fuses work, too much current and the fuse wire melts breaking the circuit
You may also like to know that if the voltage is high enough it will actualy fry what ever it is passing through, so that is why you sometimes hear of people suffering from from burns when they get an electric shock.
Gruesome but true:
people who are sent to the electric chair are often fried due to their resistance rather than electrocuted.
Also the higher the voltage the more it can "jump" so that is why "overhead lines" are so high up, so they cant jump to you, which is why you should NEVER climb a pylon, because as you get near it the electricity will jump to you and.........say no more.
a typical pylon runs at 33,000 volts although some are higher and some lower . The household supply is only 230v and a battery is only 1.5 v, so you can see the major difference.
ac or dc (alternatiing or direct current)
In short alternating current keeps changing direct current does not
if you touch an alternating current it puts your muscles into spasam (tingles) and if you touch a wire it will "throw you"
if you touch a dc current it will "hold" your muscles and keep you there, so you may also die of suffocation since your muscles can not move (you can't breathe) that is why your house supply is ac not dc as although both will kill ac is slightly safer. not to mention it is easier to "transport" ac across the country as opposed to using dc. (another "useless" thread later maybe)
Please remember the above although true does not go into the exact details and principlas of what is involved, it is just a basic outline.
so remember if you are not sure ASK or better still get a qualified electrician, not some one who "knows a bit" as what they do is probaly dangerous.
Earthing and rcd's etc are also not mentioned as you didn't ask and it would have made this post even longer. but in very short terms
anything metal must be earthed for saftey sake unless it is double insulated
Breezer, introducing an earth into an otherwise earth free enviroment can just as dangerous as not earthing in an enviroment with earths
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Well Edison was all for DC supplies, had a commercial interest in it being adopted, and tried to convince the American public by electrocuting animals with AC at a touring "show"! He persuaded the authorities to use AC for the Electric Chair, to try to turn people against it (Westinghouse were advocating AC) but in the end he lost! Thank goodness for that...plugwash said:
Cheers,
Howard
yawn
Reminds me a few years ago i was chatting to a bloke from the national grid and he was telling me that they hed a new chap start that day. They had a job to do on the pylons and were being dropped in by helicopter. The two exprienced guys put their hands out when nearing the cables and realised equipotential, The new guy was too frightened and wouldn't put out his hands so when they got close enough the potential jumped and took out all of his fillings.
Just what I was told, it may be an "urban myth"
Just what I was told, it may be an "urban myth"
B
breezer
urban myth i am affaraid to say.
they all go on training first.
they also get "zapped" by a "few thousand volts" and it does make your hair stand on end though
they all go on training first.
they also get "zapped" by a "few thousand volts" and it does make your hair stand on end though
Is not AC more dangerous than DC?
Hence Low voltage = 1500v DC or 1000v Ac & ELV = 50v AC or 120v ripple free DC.
I should have asked the opposite question - what voltage is safe?
Hence Low voltage = 1500v DC or 1000v Ac & ELV = 50v AC or 120v ripple free DC.
I should have asked the opposite question - what voltage is safe?
B
breezer
ebee said:
I really wonder why i bothered
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Because you're kind enough to care and you took the trouble to make it easier to read!
However you forgot that some won't listen and won't read more than 9 words.
BTW That's why the "Sun" newspaper never has a sentence with more than 9 words. They understand their marketplace.
However you forgot that some won't listen and won't read more than 9 words.
BTW That's why the "Sun" newspaper never has a sentence with more than 9 words. They understand their marketplace.
B
breezer
SwindonSpark said:
Very fair and very kind of you. thank you
Is 70 Volts Dangerous then?
Considering what has already been written in this thread I would think you have been given adequate information.
I suggest you experiment ..........
I suggest you experiment ..........
ebee said:
i think the reason for that is what they really care about in making that distinction is absoloute maximum voltage rather than rms voltage but if they specified it that way they would confuse people
1000v AC rms is about 1500V ac peak
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