Usually, dry skin has a high resistance, so the current from voltages upto about 1kV is limited by the resistance of the skin. So the danger is sort of proportional to the voltage. I can tell you from experience, several times, that only a few hundred volts is enough to give a very very bad shock though, and people have died from shocks of only a few hundred volts: its the usual cause of electrocution, because these lower voltages are usual in ordinary mains electricity supply, 110 volts or 141 volts peak in North America, and 240 (or 220 or 230V) volts or about 340 volts peak in many other places. Voltages higher than this (of the order of kV) can be worse because the skin is a non-linear resitance: there is dielectric breakdown at this voltage and the resistance is lower. Once you get through the skin, the resistance of the rest of the body is quite low (it is mostly water with dissolved ion, i.e. salty water, which is a very good conductor), so the current could be quite high. 100s of milliaperes is prety nasty, amperes of current means severe injury (burns). Current thorugh the brain or any other major organ or central nervous system is basically a death sentance. High votlages to very high voltages (10s of kilovolts up) can cause arcs to flash over the surface of the skin/body, so current through the body is small, so counterintuitively less deadly (i still dont like you chances if you touch a 66kV transmission line.....) this is quite true for lightning too: is the circumstances are favourable, you probably wont die from a lightning strike (tens of thousands of volts, tens of thousands of amps), but it will hurt very much....
It usually boils down to the energy delivered by a shock as to how bad it is. The energy delivered will depend on the energy availible from the source and how it contacts/enters your body (dry skin/wet skin etc). A 240 volt mains supply has plenty of energy avaible, but if you lightly brush it with dry hands the resistance will be high, you may only feel a tingle. A few volts (from a battery say) connected to needles which peirce the skin could kill you dead instantly.\
The lowest known voltage which has killed someone by contact (not piercing the skin) is a 32 volt DC lighting circuit, touched with wet hands. At least one man (Roy Sullivan) was struck by lightning 8 seperate times and lived all 8 times (10s of thousands of volts).
You are correct to some extent, that there is a safe limit of current passing through the body. This limit is about 8 millipedes (8 mA or 0.008 amps). Skin resistance can vary considerably, and the resistance of subdural tissue, or tissue under the skin, is far lower than skin resistance. Skin resistance is generally about 100,000 ohms directly through the skin, but moist skin, especially sweaty skin, can reduce this resistance considerably. With 100,000 ohm skin resistance, a voltage of 800 volts could result in a current of 8 mA. You could safely apply a much higher voltage as long as the voltage source is current regulated or limited so that output current cannot exceed about 5 mA (will within maximum safe current).
You can safely touch the electrodes of some high voltage insulation testers that may apply up to 100,000 volts because the output is limited to an extremely low and safe current level. But beware; most insulation testers and other high voltage devices do not have this built-in safeguard.
You are correct. If you had 10,000 volts running through you at 0.0001 amps, you almost not feel it. On the other hand, take a fresh new 9-Volt battery, and put both "buttons" in your tongue at the same tim. You WILL put the battery down now!
Items like Defibrillators work at voltages in the 1000 - 2500 VOLT range, but are designed to supply a limited current to "shock" the heart into operation.
But YOU need to understand Ohms Law, which says that, for a given VOLTAGE, the CURRENT is limited by the RESISTANCE. EVERYTHING has resistance, even a simple piece of wire, and even a human body.
Defibrillators are typically designed to accommodate a typical human resistance of about 75 ohms, and the internal circuitry is designed to LIMIT the current flowing through the body.
But there are many things that affect the resistance of the body -- large amounts of body hair versus very smooth skin, very dry versus sweaty skin, and so on. So the defibrillator machine is ADJUSTABLE, and the technician needs to be TRAINED so that the machine is adjusted so as to not let TOO MUCH current flow, and thus kill the patient.
Here are some comparisons to look at:
Wall Socket: 120 volts, current limit: 10-20 Amps. Result of shock: DEATH
TASER Gun: 5,000 volts. Current limit: Small Current. Result of shock: Loss of muscle control, Victim incapacitated, but not otherwise damaged
Static Electricity (1/4-inch spark): About 30,000 volts. Current limit: Greatly limited current, almost infinite resistance. Result of shock: Victim surprised, but not damage.
Ligntning Strike: 100,000 volts or more. Current limit: ALmost unlimited; 75 ohms (human body). Result of shock: severe burns and damage; often death.
that is not what it means when it says amps are dangerous not volts
10,000 volts when sent through a regular humans body will generate alot of amperage ... and thus will do alot of damage
you can have high frequency voltages pass over and around the body without doing much damage.. this is what happens with the tesla coils.. where the spark travels from the coil to your hand... and it just tingles a little..
if you take a flourescent light bulb and hold it and then put the other end near the TESLA coil it will cause the light to glow.. this is because the electrons are travelling through the bulb exciting the gas and then exiting through the other end and travelling through your body..to ground.. you are part of the circuit...
the voltages there are high like in the 10,000 volt range but the frequency is so high that the rms voltages are very low... and thus the current that is passing through your body SEEMS low..
when working with anything electrical keep ONE HAND in your pocket and play with your money ... that way if you touch something live it doesnt travel through your hand and through your chest and back out the other hand..
best advice is to not FOOL with electricity it is not completely safe to fool with anything from 120 volt household voltages or higher..
A car ignition system has high voltage in thousands with low amperage, due to low charge. Often people get shocked with it but nobody get killed.
If amps are dangerous and not volts then could you have 10,000 volts go through you at like .0001 amps and be ok? On that not is there a limit to the number of volts that could go through you with very little amps and still be ok?
