Mythbusters

[Jabbajaws]

Has anyone seen the experiment on Mythbusters where they investigate, whether or not a person would die, if a person was having a bath and an electrical appliance were to to fall in the water?

It was very interesting, though it has raised certain questions. Let me give you the facts.


The Mythbuster Scientists constructed a special bathroom for safety & also testing reasons.

A dummy was cast from Ballistic Gel (whatever that is) as it is supposed to be the closest artificial substance that resembles human flesh.

The dummy was then placed in the bathtub, full of water.

Above the bath was a collapseable shelf, on which the appliance being tested was placed, and this shelf was activated by a 6V relay.

The bath was grounded, as americans refer to it, otherwise known as bonding to us, so that the ammeter, that was placed around the earthed bonding wire (attached to the metal framework of the bath) would measure the amount of mA that would flow to earth, during the test.

They were advised that 70mA was enough to cause death. After performing several experiments, they sought advice from a professional electrical expert, as they called him.

He then told them that a mere 6mA travelling across the human heart is enough to cause death.

They then inserted two copper plates, one either side of the dummy's "heart" and attached a test lead to both plates, which led to an unidentified test instrument that l couldnt make out what it was.

They then proceeded to drop several appliances into the bath, measuring the amount of mA across the plates, as they had been told that 6mA across the heart causes death.

I am confused by this. This appears to look more like capacitance than an amperage measurement to me.

Can anyone explain this to me, how they can measure amps across the 'heart' by using copper plates? I just dont get this.

And can anyone support the '6mA across the heart is likely to cause death argument'? Im sure thats wrong....

 

[aptsys]

That test was full of flaws, but I humoured them through that episode. They more than likely were measuring the voltage across the two plates, which would allow them to estimate the current flowing through the heart (if they estimate the resistivity of human flesh). They could not measure current directly just using two plates like that.

Current isn't the decider of lethality anyway - they should have been measuring energy.

 

[acat]

A mate of mine when we were at school tinkered with his mothers washing machine and got a belt that left him with scarred tissue the size of a football on his chest and he lived

Chris

 

[GrannySmiff]

With regard to the 6mA I was told that somewhere around there would fry your heart but as the human body is vast fat, muscle, etc the mA is spread out so 70mA to the body and maybe only 6mA makes it direct to the heart if that makes sense.

Something like that anyway.

 

[pushrod]

And can anyone support the '6mA across the heart is likely to cause death argument'? Im sure thats wrong....

With these things there is never an exact figure applicable to all, only averages and max and min values . It might be possible that 6mA could kill one person ( maybe a small child) but it would be very unlikely to kill a large adult. The figure that i most usually come across is 50mA being sufficient to possibly cause death, although the route the current takes through the body would be very significant. I am sure, for example, that 100mA across the hand would be much less life-threatening than 10mA across heart!