High voltage currents of 500 V and more can cause deep burns, while low voltage currents consisting of 110–120 V can result in muscle spasms. A person can get an electric shock through contact with an electric current from a small household appliance, wall outlet, or extension cord.
The human body has an inherent high resistance to electric current, which means without sufficient voltage a dangerous amount of current cannot flow through the body and cause injury or death. As a rough rule of thumb, more than fifty volts is sufficient to drive a potentially lethal current through the body.
You may lose your balance and fall, which can cause injury or even death if you fall into machinery that can crush you. High voltages can also cause severe burns (as seen on pages 9 and 10). At 600 volts, the current through the body may be as great as 4 amps, causing damage to internal organs such as the heart.
Voltages greater than 450V a.c. are especially dangerous. At this point the resistance of the skin can break down which significantly reduces the body's overall resistance thereby causing a substantial increase in current.
An electrical current at 1,000 volts is no more deadly than a current at 100 volts. But tiny changes in a current's amperage can mean the difference between life and death when a person receives an electrical shock.
450V is certainly enough to deliver a fatal current, but it needs to be sustained. It seems that it would require about 500ma for 100 milliseconds to deliver a charge which is likely to cause heart fibrillation using normal skin contact from a limb to earth (a lot depends on the exact path taken).
It is sometimes suggested that human lethality is most common with alternating current at 100–250 volts; however, death has occurred below this range, with supplies as low as 42 volts.
Thus, in the absence of high voltage, flowing current cannot flow through the body or cause injury or death. For example, a shock of 20,000 volts is passed through the body but the current is extremely low and duration is short, the shock would be harmless.
It can also cause burns, respiratory failure, cardiac arrest, and other serious injuries or death. 7000 volts of electricity can be extremely dangerous and potentially deadly to humans.
"If a healthy person receives a shock of 5,000 volts, they may die on the spot. "In the case of this frozen patient, the task seemed impossible." By comparison in the use of execution by electrocution, a jolt of 2,000 volts is typically used, destroying the brain, followed by shocks with a lessor voltage.
A good rule of thumb is that when a shock is at or above 2,700 volts, it often results in death or severe injury. At over 11,000 volts, the victim will usually pass away. A good rule of thumb is that when a shock is at or above 2,700 volts, the person often dies or experiences severe injury.
That said, 480V can kill and should be handled with extreme care. Accidents do unfortunately happen but any electrician should and will try minimise that risk.
Witness testimony, botched electrocutions (see Willie Francis and Allen Lee Davis), and post-mortem examinations suggest that execution by electric chair is often painful.
However, lest these details be misinterpreted, the only reasonable conclusion that can be drawn is that 75 volts are just as lethal as 750 volts. The actual resistance of the body varies depending upon the points of contact and the skin condition (moist or dry).
At 600 volts, the current through the body may be as great as 4 amps, causing damage to internal organs, such as the heart. High voltages also produce burns. In addition, internal blood vessels may clot. Nerves in the area of the contact point may be damaged.
12V isn't a shock hazard, but it IS a burn hazard.
Even without a short circuit, if you make or break an electrical connection that has a lot of current going through it, the point at which the connection is made can get very hot very quickly and can burn your fingers.
Dr. Michael S. Morse, a professor of electrical engineering at the University of San Diego, explains that while 10,000 volts can be life threatening in certain circumstances, it's possible for something to have 10,000 volts behind it and be relatively harmless.
Of course 25 KV is lethal but it actually depends upon how much current it will send through human body. As mentioned in earlier answers, if you are hanging on 25KV power line, nothing will happen but if any of your body part touches to earth, it will roast you in to the ashes.
They were divided into four groups, and five second shocks of 50,000 volts were administered to two of them. The researchers found "statistically significant reductions" in verbal learning and memory; some participants also had trouble concentrating, and they felt overwhelmed and anxious.
A typical lightning flash is about 300 million Volts and about 30,000 Amps. In comparison, household current is 120 Volts and 15 Amps.
Voltage and Amperage
High voltages greater than 500-1000 Volts cause deep burns and extensive deep tissue and organ damage. Low voltage exposures tend to result in lesser injury.
120v/100,000Ω=0.0012 amperes which equals 1.2mA. A person may feel a slight tingling sensation. The severity of shock from a given source will depend upon its path through your body.
Know that any amount of current over 10 milliamps (0.01 amp) is capable of producing painful to severe shock, and currents between 100 and 200 mA (0.1 to 0.2 amp) are fatal. Anything higher than 300mA is fatal and kills in seconds. 4.5 to 10A will instantly lead to cardiac arrest, severe burns and finally death.
Contact with both live wires of a 240-volt cable will deliver a shock. (This type of shock can occur because one live wire may be at +120 volts while the other is at -120 volts during an alternating current cycle—a difference of 240 volts.).
Loss of consciousness. Muscle spasms. Breathing difficulties (or no breathing) Numbness / Tingling.