Voltage and ampage - Is this correct?

[NewOrder]

My understanding of this has always been that it is the voltage that kills you, but in order to have a have enough force you need ampage as well. E.g 10,000 volts at 1 milliamp cannot hurt you. Yet 60amps at 12v could do quite a bit of damage, but not as much as say 240v at 13amps.

E.g voltage is the amount of current you have, e.g how fast the electrons are flowing but the ampage is the actual force, e.g the actual weight of it.

Could anybody explain this is more simple english?

 

[davy_owen_88]

It's not one thing that kills you, its really a combination of three things. You 'need' sufficient current to flow through the heart for it to stop (I can't remember how much exactly but its very low, the more current the more likely your heart will stop). For sufficient current to flow you need to have a low enough resistance for the given voltage, the higher the voltage the lower the resistance needs to be. So your first example is correct (1mA is probably not going to kill no matter what the voltage) but the second and third are wrong - the more current that flows the more likely your heart is going to stop beating and then you die...)

It's just basic ohms law...

V = I x R ... R = V / I ... I = V / R

Say your resistance to earth is 20 ohms (ignoring all safety devices) and you get zapped at 240V, 12A will flow through you.

240 / 20 = 12A

If you were standing up a fibreglass ladder then your resistance should be very high so at 240V with a resistance of 20Mohms you'd only get 0.000012A or 0.012mA flowing through you, besides a slight tingle you'd probably be fine.

240 / 20,000,000 = 0.012mA

If you were up the same ladder but touched a live conductor at 66kV you'd get 0.033A or 33mA through you - this is enough to kill you.

66,000 / 20,000,000 = 33mA

Any help?

 

[ban-all-sheds]

voltage is the amount of current you have,

No - voltage is voltage and current is current - they are two different things. The unit of voltage is the volt, and the unit of current is the ampere, and they are related to each other in the way described by Ohm.

 

[breezer]

My understanding of this has always been that it is the voltage that kills you,

nope, its the current that kills you.

I believe its about 8 mA measured across the heart that will kill you.

thats why people who go to the electric chair actually fry, the voltage is not enough to carry 8 mA across the heart, but it does "warm up" the conductor due to the high resistance.

The conductor being the person sitiing in the electric chair in this case

 

[ban-all-sheds]

thats why people who go to the electric chair actually fry, the voltage is not enough to carry 8 mA across the heart

It's 2kV..

 

[disinfo]

My understanding of this has always been that it is the voltage that kills you,

I believe its about 8 mA measured across the heart that will kill you.

Isnt this more like 80mA as it puts the heart into ventricular fibrillation?

 

[breezer]

as for how much current across the heart to kill, it is now generally accepted to be around 8-12 mA

clicky

obviously it depends on skin resistance where electrodes are etc. but since its dpoubtfull there will be any volunteers to try and find it out for sure we will never be able to to tell exactly.


the electric chair voltage varies acording to where you ask.

some say they start at a low voltage and the voltage is increased, but as i said it depends on where you ask, but upto around 2k does seem to be what most say.

but you still need to get 8 -12 mA across the heart and if the persons resitance is too high it isnt going to happen.

Any one reading thios should also bear in mind people have been killed accidentaly with less voltage.

Remember. Electricity has no prejudices, it kills any one

 

[Master of None]

If you were standing up a fibreglass ladder then your resistance should be very high so at 240V with a resistance of 20Mohms you'd only get 0.000012A or 0.012mA flowing through you, besides a slight tingle you'd probably be fine.

240 / 20,000,000 = 0.012mA

I am not an electrician but I understand the math. However are you really immune to electrocution if you are well insulated. Could the act of charging the body ie. capacitance not in certain circumstanced pass the magic 30mA across your heart an stop it. I now realise why electricians use the very heavy fibre glass steps instead of the feather light aluminium. interesting.

 

[breezer]

no you dont.

its mostly so they cant lift it to move it and so touch something live. I believe It started on railway stations

oh and 30mA is not magic, its just the tripping current of most domestic RCD's

 

[Master of None]

oh and 30mA is not magic, its just the tripping current of most domestic RCD's

I know its not magic but I thought that was why domestic RCD's were rated at 30mA because any more is lightly to stop your heart.

Guess thats why sparrows can sit on overhead lines.

By the way did any one see that news report a while ago about the pilot who got his light aircraft tangeled in overhead lines and hung there for ages and was ok. looky bliter.

They must have quite a breaking strain. Any one know what sort of diameter they are close up?

 

[davy_owen_88]

oh and 30mA is not magic, its just the tripping current of most domestic RCD's

I know its not magic but I thought that was why domestic RCD's were rated at 30mA because any more is lightly to stop your heart.

I think its also to do with duration. 30mA for <200ms (max permitted tripping time at rated value) must have been tested and confirmed to be unlikely to stop a human heart. 8mA might be able to do it, but only when the current is sustained for a longer period of time.

 

[Master of None]

Wonder who they tested that on. Did they start low and gradually ramp up. Or did they have plenty of volunteers and start at full belt and work down.

 

[ban-all-sheds]

It varies from person to person, and for any given person it varies from time to time, depending on their skin and body moisture content, for some women it varies according to the time of the month, and for everyone it varies depending on which parts of the body are used to make contact and how - two fingers of the same hand lightly touching L & E are going to be less of a problem than one finger from each hand firmly pressed.

AFAIK 30mA was chosen as the best compromise between safe enough for enough people enough of the time and so sensitive that nuisance trips become unreasonable.

There are some high sensitivity environments where less than 30mA is required.

 

[ban-all-sheds]

They must have quite a breaking strain. Any one know what sort of diameter they are close up?

This guy does....

 

[333rocky333]

would it be possible to kill someone with a megger then.