I routinely used 800 amp welders at 12 -20V to weld heavy steel plate and would grab the electrodes with the welder on to change the electrodes and never felt a shock....until one day when I was sweating pretty bad and it made my gloves wet so when I took them off to change rods, my sweaty hand gave me a very strong shock that made me more nauseated because it wasn't the sharp pain you feel from an AC frequency shock it was more of feeling like the electricity was doing electrolysis to me inside organs and making my heart into an anode and plating out on to my stomach as a cathode.....literally like my body parts were dissociating inside me..
So to make it a short story, low voltage at high amperage isn't harmful...unless you make yourself a better conductor with water or salts of some kind. Just wear dry gloves and no problem.
The way you are killed is to have enough voltage to overcome your skin resistance and then if you have amperage volume of power behind that voltage...then you get hurt or die. But normally 12 volts won't hurt you. People grab their battery car terminals all the time and they have 700 amps or more and you don't fill a shock. Don't try it though if you dip your hands in a pickle jar and get that nice electrolyte of salt and acid on your fingers because it will lower your skin resistance so much , that touching the battery terminals could kill you or give you a heart attack
As was said above several times, Ohm's law. It takes about 10milliamps of current through your body to start becomming a serious problem. BUT, voltage is needed to push that current. Your skin has the highest resistance in your body, and makes the resistance of your body about 10KΩ under normal circumstances. So even thought a source may be capable of 100amps, 10,000 times what it takes to hurt you, if the voltage is low the full current capability of the source won't flow.
50V into 10KΩ is 5mA. But your skin resistance varies a lot depending on how wet it is and how thick the skin is. The skin on the bottom of your foot is about 10 times thicker than on the inside or your forearm, for example. If you're standing in salt water, that 10K can easily go down to a few hundred Ohms. And now 30V can give you a dangerous shock.
Sure, the lower the voltage, the less your chances of getting a shock. But then there are other considerations. Low voltage power means more current and bigger wires. Sometimes that's OK. Sometimes it makes things too bulky and/or expensive.
It is voltage that causes a shock, because it is applied across the resistance of the body. However, the severity of the shock depends on the current. 10 volts will not cause enough current to give you a noticeable shock. However, 100 amps at 10 volts is 1000 watts and this is a lot of heat.
If you've got an input (primary) current limited to (say) 1 amp, then the output (secondary) current is limited to 100 amps.
OK.
But for a given resistance across the secondary (eg you;) the lower voltage across the secondary means that the current will be lower than if you put yourself across the primary. Remember Ohm's law:
Current = voltage/resistance.
The act of transforming down to a lower voltage does *not* mean that the current will increase for a given resistance.
A transformer changes the power rating. when the voltage goes down the current available goes up. It only delivers the current that a connected devise requires. 50 miliamps can killl you.
The saying is, Its the volts that jolts but the amps that kill.
It's actually a 100 times DECREASE in amperage. Whatever amperage is caused on the 10 volt side, there is only 1/100th as much on the high-voltage side.
No, the electrical Resistance of your body do not allow high amperage passage by applying just 10 V.
Let's say that you have a transformer of a 100:1 ratio. You put 1000 volts into it and it is reduced to 10 volts on the other secondary side. They say that less than 50 volts is non lethal. What about the 100 increase in amperage? Can that kill you?
