So this reminds me of a topic of discussion during a college class at which I was in attendance. The discussion started when one student pulled a 9v battery out of an electronic device and licked the electrodes āto see if itās any goodā. Several others had never heard of such a thing, or thought it would really hurt, so discussions ensued. Then came the āif you had a tongue that long, can you lick a car battery?ā question. All but 1 person in the room asserted that it would almost surely kill you, since car batteries are so much bigger than the little 9v which āproduces a tingle on the tongueā. Which side would you be on, and why?
(Yeah, this IS pretty elementary, but for non-electronically inclined folks, I wonder if your ellucidation might be helpful. No matter what is asserted or postulated here, please donāt actually DO any of this at home! Get your friends to do it, and be sure to video and post back. (thatās sarcasm, folks. Really, donāt anyone attempt any of this at home) )
The crux of what kills you generally is the current that flows across your heart. Much like a defibrillator in reverse.
Have never put my tongue across the terminals of a car battery, but have seen a safety video where a āmechanicā wearing a dangling necklace had the necklace make contact with both terminals. Weld itself to those terminals and proceed to discharge through said mechanic. Didnāt end well.
That said, we could always do a Mythbusters, and get a dummy made from balistics gel and some electrodes and do some empirical measurements. Sounds like an activity for the Science committeeā¦
Some folks in the class had seen similar videos. It appears they learned ācar batteries are dangerousā instead of the actual lesson (assuming it was an educational video) which is generally INTENDED to be āDo NOT wear jewellery while working with electricity, including car batteriesā.
I got no funds, but Iām all in favor of the proposalā¦
A 9 Volt battery discharging across a wet tongue probably produces about 10 mA of current
I = V/R = 9 / 1k ~ 10 mA
and so P = IV = 10 mA * 9 V = 90 mW
A 12 V car battery would produce a little more current and a little more power, but I doubt it would kill you. Your tongue probably would hurt a lot, though.
Iād be more worried about the sulfuric acid, lead and other nasty chemicals on the battery.
A 9v battery has an extremely high ESR, which drastically reduces the amount of current it can deliver. On the other hand, a car batter has very little ESR, so can deliver extremely large ammounts of current.
Your āestimatesā of bodily resistance is flawed. For instance, if you would put two jumper cables across your tongue you would be creating essentially a dead short, since you have a conductive liquid on the surface. With enough current to cook your tongue.
Easy to determine how correct your expectation of resistance of the tongue would be. Just use hookup wire, a 9v battery, and a meter. Might make a good demonstration for the open house.
A lot depends upon the conductivity of the circuit. Your tongue is more conductive and sensitive than other parts of your anatomy such as your hand so the current flow is more through your tongue. Put a much more conductive solution in your mouth like salt water then put your tongue out and try it.
Ever see those shows where a battery bank and jumper cables are used to torture a poor soul who has been doused with water? Canāt say it would kill you but the pain would be intense.
Lastly, my wife has a TENS unit for medical reasons and it uses a little ole 9V battery, but due to the amplification circuitry can inflict some serious pain on the highest setting. So can a cattle prod for that matter, so the size of the battery isnāt the real issue.
Walter is right it is the current across the heart that kills you. Either that or your organs, limbs etc being cooked due to the high current and voltage, like on a power line. They were probably dead before they cooked, but still the cooking wasnāt good for them either.
These are rather morbid thoughts, but honestly the most effective safety videos I ever showed in the Air Force were of guys getting hurt, maimed or killed while doing something they shouldnāt have been doing according to the USAF Tech Orders. We should continually focus on safety and help our fellow members when we see them doing something unsafe.
Actually, I donāt have a source, but by reducing R you get more current (I) so anything such as additional salinity should increase the current right? The more ions the better the conductivity right?
Several sources state that human body electrical resistance varies from about 1k-ohm to 100k-ohm. Iām using the lowest value as an estimate, for a starting point. Feel free to use whatever value you feel is reasonable. Iām certain that no part of the natural human body has an electrical resistance as low as a 12-gauge copper wire, or a piece of metal jewelry.
Hell, I will still do the 9 volt battery to the tongue. I did that as recent as Tuesday when I was checking to be sure it was a good battery. Anyone care to be a guinea pig with a megger to test the resistance? lol
I am fairly certain that you are mistaken. Our blood has a very similar conductivity as a salt solution of similar concentration. Which is a VERY low resistance. It is why currents introduced below the skin (which provides a great deal of electrical insulation) is so much more dangerous.
Your tongue is bathed in a similar electrolyte solution, which further increases itās conductivity. I would guess well little more than 0.01 siemens.
The OP described procedure is largely safe because the high ESR of 9V batteries significantly limits the current those sources can provide.
Further, it is important to recognize the path the current flows through. So for instance, when you shocked yourself with the capacitor, the path was through your body, then your socks, then your shoes, and finally through the concrete to an earth ground.
The 9V path (or presumably the 12V car batteries path) would be across an inch or two of your highly conductive tongue, since the āground returnā would be the negative terminal of the battery and not an earth ground. This low resistance would allow a lot of current to flow in a source that is capable of delivering it (which a 9V battery is not). That current would then produce a lot of heat dissipation.
A reasonable mockup of what might happen could be demonstrated with a moderately moist host dog and two nails, and a pair of jumper cables.
As a kid I had a electric hot dog cooker, which was basically two electrodes that you stuck each end of a hotdog into, put on the lid, and it ran 120vac through the dog and cooked it in about a minute. So I donāt thing these things are too conductive to spontaneously combust at 12v.
Hereās some elementary school level science on licking a 9v.
According to Ohmās law, I=V/R, so using their numbers, change V from 9 to 12 and there ya goā¦
Thoughts?
For those of you with no patience for reading, hereās the accompanying video. It does not address the whole article, butā¦