Fresh Water vs Salt Water Electrocution potential

[Scott Sease]

During a recent PE class, I saw a Mike Holt DVD where he and the panel discussed the Electrocution Potential of fresh Water versus Salt Water. Mike stated that Fresh Water had more potential and and could create a deadlier situation than a likewise scenario with Saltwater. He went through it so fast that I could not grasp it enough to explain it when talking to somebody else. Does anybody have a 'bare-bones" explanation of why this is so? In Missouri, right after we saw that DVD, we had a couple of fatalities involving some kids who jumped in a fresh water lake and were electrocuted when they swam near the dock. As far as I know, they are still trying to confirm where the fatal source voltage came from.

 

[charlie tuna]

just my oppinion---the salt water is very low in resistance -- lower than the body --- so if you got between the source voltage and ground the potential would be carried by the salt water.
on fresh water -- it has a higher resistance than a body -- so the current would flow through the body and not the fresh water.

pure water is an insulator!!!

 

[tom baker]

That was Mikes Grounding vs Bonding. Salt Water is more conductive so there is less voltage gradient. Fresh water is less conductive and there is a large gradient, IE it may take 100 ft for the 120v to drop to 0. Plus if you will recall most water electrocutions are due to drownings.

 

[charlie b]

Does anybody have a 'bare-bones" explanation of why this is so?

Think "current divider." Think about two resistors, one being the human body. Think of two "thought experiments" (don't try this at home!), using the same human body and the same resistance value for that body.

Put the body in parallel with one resistor (i.e., salt water), and impose a voltage source on both.

Put the body in parallel with another resistor of a higher value (i.e., fresh water), and impose the same voltage source on both.

In which case will the amount of current in the human body be higher,
(1) The case that has a low resistance in parallel, or
(2) The case that has a higher resistance in parallel?